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Comparing Eisenhower’s D-Day Writings

General Dwight D. Eisenhower gave the final order that put the vast D-day operation in motion on June 5, 1944, after a break in the stormy weather was predicted for the next day. Following his decision, Eisenhower dashed off this note, in case the Allied invasion of Europe on D-Day (June 6th) failed. In the statement, he praised the men under his command and claimed that any fault or failure “is mine alone.” The only apparent hint of nerves on his part is his error in dating the note “July 5” instead of June 5.

Transcript of note (picture on the right):

Our landings in the Cherbourg-Havre area have failed to gain a satisfactory foothold and I have withdrawn the troops. My decision to attack at this time and place was based upon the best information available. The troops, the air and the Navy did all that Bravery and devotion to duty could do. If any blame or fault attaches to the attempt it is mine alone.

The original letter written by General Eisenhower in case the invasion was unsuccessful (transcript above).
Actual message from General Eisenhower (courtesy of National Archives).

Transcript of Eisenhower’s Message (figure on the right):

SUPREME HEADQUARTERS
ALLIED EXPEDITIONARY FORCE

Soldiers, Sailors, and Airmen of the Allied Expeditionary Force!

You are about to embark upon the Great Crusade, toward which we have striven these many months. The eyes of the world are upon you. The hope and prayers of liberty-loving people everywhere march with you. In company with our brave Allies and brothers-in-arms on other Fronts, you will bring about the destruction of the German war machine, the elimination of Nazi tyranny over the oppressed peoples of Europe, and security for ourselves in a free world.

Your task will not be an easy one. Your enemy is will trained, well equipped and battle-hardened. He will fight savagely.

But this is the year 1944! Much has happened since the Nazi triumphs of 1940-41. The United Nations have inflicted upon the Germans great defeats, in open battle, man-to-man. Our air offensive has seriously reduced their strength in the air and their capacity to wage war on the ground. Our Home Fronts have given us an overwhelming superiority in weapons and munitions of war, and placed at our disposal great reserves of trained fighting men. The tide has turned! The free men of the world are marching together to Victory!

I have full confidence in your courage, devotion to duty and skill in battle. We will accept nothing less than full Victory!

Good luck! And let us beseech the blessing of Almighty God upon this great and noble undertaking.

[signature]

Citations:

  • “In Case of Failure” Message Drafted by General Dwight Eisenhower in Case the D-Day Invasion Failed; 6/5/1944; Principal Files, 1916 – 1952; Collection DDE-EPRE: Eisenhower, Dwight D: Papers, Pre-Presidential; Dwight D. Eisenhower Library, Abilene, KS. [Online Version, https://www.docsteach.org/documents/document/in-case-of-failure, January 18, 2020]
  • D-Day Statement to Soldiers, Sailors, and Airmen of the Allied Expeditionary Force; 6/1944; Principal Files, 1916 – 1952; Collection DDE-EPRE: Eisenhower, Dwight D: Papers, Pre-Presidential; Dwight D. Eisenhower Library, Abilene, KS. [Online Version, https://www.docsteach.org/documents/document/dday-statement, January 18, 2020]

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Eisenhower’s D-Day Message

This statement from General Dwight D. Eisenhower encouraged Allied soldiers, sailors, and airmen taking part in the D-day invasion. It was handed to Allied troops stepping onto their transports on the eve of the cross-channel assault into Normandy. As Commander of the Supreme Headquarters, Allied Expeditionary Force, Eisenhower provided hope for those about to liberate the European continent from Nazi tyranny.

Actual message from General Eisenhower (courtesy of National Archives).

Against a tense backdrop of uncertain weather forecasts, disagreements in strategy, and related timing dilemmas predicated on the need for optimal tidal conditions, Eisenhower decided before dawn on June 5 to proceed with Overlord. Later that same afternoon, he scribbled a note intended for release, accepting responsibility for the decision to launch the invasion and full blame, should the effort to create a beachhead on the Normandy coast fail.

Much more polished is this printed Order of the Day for June 6, 1944, which Eisenhower began drafting in February. The order was distributed to the 175,000-member expeditionary force on the eve of the invasion.

Transcript of Eisenhower’s Message

SUPREME HEADQUARTERS
ALLIED EXPEDITIONARY FORCE

Soldiers, Sailors, and Airmen of the Allied Expeditionary Force!

You are about to embark upon the Great Crusade, toward which we have striven these many months. The eyes of the world are upon you. The hope and prayers of liberty-loving people everywhere march with you. In company with our brave Allies and brothers-in-arms on other Fronts, you will bring about the destruction of the German war machine, the elimination of Nazi tyranny over the oppressed peoples of Europe, and security for ourselves in a free world.

Your task will not be an easy one. Your enemy is will trained, well equipped and battle-hardened. He will fight savagely.

But this is the year 1944! Much has happened since the Nazi triumphs of 1940-41. The United Nations have inflicted upon the Germans great defeats, in open battle, man-to-man. Our air offensive has seriously reduced their strength in the air and their capacity to wage war on the ground. Our Home Fronts have given us an overwhelming superiority in weapons and munitions of war, and placed at our disposal great reserves of trained fighting men. The tide has turned! The free men of the world are marching together to Victory!

I have full confidence in your courage, devotion to duty and skill in battle. We will accept nothing less than full Victory!

Good luck! And let us beseech the blessing of Almighty God upon this great and noble undertaking.

[signature]

Citation: D-Day Statement to Soldiers, Sailors, and Airmen of the Allied Expeditionary Force; 6/1944; Principal Files, 1916 – 1952; Collection DDE-EPRE: Eisenhower, Dwight D: Papers, Pre-Presidential; Dwight D. Eisenhower Library, Abilene, KS. [Online Version, https://www.docsteach.org/documents/document/dday-statement, January 18, 2020]

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World War II – European Theater

From: Openstax College Textbook on U.S. History

WARTIME DIPLOMACY

Franklin Roosevelt entered World War II with an eye toward a new postwar world, one where the United States would succeed Britain as the leader of Western capitalist democracies, replacing the old British imperial system with one based on free trade and decolonization. The goals of the Atlantic Charter had explicitly included self-determination, self-government, and free trade. In 1941, although Roosevelt had yet to meet Soviet premier Joseph Stalin, he had confidence that he could forge a positive relationship with him, a confidence that Churchill believed was born of naiveté. These allied leaders, known as the Big Three, thrown together by the necessity to defeat common enemies, took steps towards working in concert despite their differences.

Prime Minister Winston Churchill and President Roosevelt met together multiple times during the war. One such conference was located in Casablanca, Morocco, in January 1943.

Through a series of wartime conferences, Roosevelt and the other global leaders sought to come up with a strategy to both defeat the Germans and bolster relationships among allies. In January 1943, at Casablanca, Morocco, Churchill convinced Roosevelt to delay an invasion of France in favor of an invasion of Sicily. It was also at this conference that Roosevelt enunciated the doctrine of “unconditional surrender.” Roosevelt agreed to demand an unconditional surrender from Germany and Japan to assure the Soviet Union that the United States would not negotiate a separate peace between the two belligerent states. He wanted a permanent transformation of Germany and Japan after the war. Roosevelt thought that announcing this as a specific war aim would discourage any nation or leader from seeking any negotiated armistice that would hinder efforts to reform and transform the defeated nations. Stalin, who was not at the conference, affirmed the concept of unconditional surrender when asked to do so. However, he was dismayed over the delay in establishing a “second front” along which the Americans and British would directly engage German forces in western Europe. A western front, brought about through an invasion across the English Channel, which Stalin had been demanding since 1941, offered the best means of drawing Germany away from the east. At a meeting in Tehran, Iran, also in November 1943, Churchill, Roosevelt, and Stalin met to finalize plans for a cross-channel invasion.

THE INVASION OF EUROPE

Preparing to engage the Nazis in Europe, the United States landed in North Africa in 1942. The Axis campaigns in North Africa had begun when Italy declared war on England in June 1940, and British forces had invaded the Italian colony of Libya. The Italians had responded with a counteroffensive that penetrated into Egypt, only to be defeated by the British again. In response, Hitler dispatched the Afrika Korps under General Erwin Rommel, and the outcome of the situation was in doubt until shortly before American forces joined the British.

Although the Allied campaign secured control of the southern Mediterranean and preserved Egypt and the Suez Canal for the British, Stalin and the Soviets were still engaging hundreds of German divisions in bitter struggles at Stalingrad and Leningrad. The invasion of North Africa did nothing to draw German troops away from the Soviet Union. An invasion of Europe by way of Italy, which is what the British and American campaign in North Africa laid the ground for, pulled a few German divisions away from their Russian targets. But while Stalin urged his allies to invade France, British and American troops pursued the defeat of Mussolini’s Italy. This choice greatly frustrated Stalin, who felt that British interests were taking precedence over the agony that the Soviet Union was enduring at the hands of the invading German army. However, Churchill saw Italy as the vulnerable underbelly of Europe and believed that Italian support for Mussolini was waning, suggesting that victory there might be relatively easy. Moreover, Churchill pointed out that if Italy were taken out of the war, then the Allies would control the Mediterranean, offering the Allies easier shipping access to both the Soviet Union and the British Far Eastern colonies.

D-Day

U.S. troops in a military landing craft approach the beach code-named “Omaha” on June 6, 1944. More than ten thousand soldiers were killed or wounded during the D-day assault along the coast of Normandy, France.

A direct assault on Nazi Germany’s “Fortress Europe” was still necessary for final victory. On June 6, 1944, the second front became a reality when Allied forces stormed the beaches of northern France on D-day. Beginning at 6:30 a.m., some twenty-four thousand British, Canadian, and American troops waded ashore along a fifty-mile piece of the Normandy coast (Figure 27.16). Well over a million troops would follow their lead. German forces on the hills and cliffs above shot at them, and once they reached the beach, they encountered barbed wire and land mines. More than ten thousand Allied soldiers were wounded or killed during the assault. Following the establishment of beachheads at Normandy, it took months of difficult fighting before Paris was liberated on August 20, 1944. The invasion did succeed in diverting German forces from the eastern front to the western front, relieving some of the pressure on Stalin’s troops. By that time, however, Russian forces had already defeated the German army at Stalingrad, an event that many consider the turning point of the war in Europe, and begun to push the Germans out of the Soviet Union.

Nazi Germany was not ready to surrender, however. On December 16, in a surprise move, the Germans threw nearly a quarter-million men at the Western Allies in an attempt to divide their armies and encircle major elements of the American forces. The struggle, known as the Battle of the Bulge, raged until the end of January. Some ninety thousand Americans were killed, wounded, or lost in action. Nevertheless, the Germans were turned back, and Hitler’s forces were so spent that they could never again mount offensive operations.

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Two Inventors: Bell (Telephone) & Edison (Light)

From: OpenStax’s U.S. History College Textbook

ALEXANDER GRAHAM BELL AND THE TELEPHONE

Alexander Graham Bell’s patent of the telephone was one of almost 700,000 U.S. patents issued between 1850 and 1900. Although the patent itself was only six pages long, including two pages of illustrations, it proved to be one of the most contested and profitable of the nineteenth century. (credit: U.S. National Archives and Records Administration)

Advancements in communications matched the pace of growth seen in industry and home life. Communication technologies were changing quickly, and they brought with them new ways for information to travel. In 1858, British and American crews laid the first transatlantic cable lines, enabling messages to pass between the United States and Europe in a matter of hours, rather than waiting the few weeks it could take for a letter to arrive by steamship. Although these initial cables worked for barely a month, they generated great interest in developing a more efficient telecommunications industry. Within twenty years, over 100,000 miles of cable crisscrossed the ocean floors, connecting all the continents. Domestically, Western Union, which controlled 80 percent of the country’s telegraph lines, operated nearly 200,000 miles of telegraph routes from coast to coast. In short, people were connected like never before, able to relay messages in minutes and hours rather than days and weeks.

One of the greatest advancements was the telephone, which Alexander Graham Bell patented in 1876. While he was not the first to invent the concept, Bell was the first one to capitalize on it; after securing the patent, he worked with financiers and businessmen to create the National Bell Telephone Company. Western Union, which had originally turned down Bell’s machine, went on to commission Thomas Edison to invent an improved version of the telephone. It is actually Edison’s version that is most like the modern telephone used today. However, Western Union, fearing a costly legal battle they were likely to lose due to Bell’s patent, ultimately sold Edison’s idea to the Bell Company. With the communications industry now largely in their control, along with an agreement from the federal government to permit such control, the Bell Company was transformed into the American Telephone and Telegraph Company, which still exists today as AT&T. By 1880, fifty thousand telephones were in use in the United States, including one at the White House. By 1900, that number had increased to 1.35 million, and hundreds of American cities had obtained local service for their citizens. Quickly and inexorably, technology was bringing the country into closer contact, changing forever the rural isolation that had defined America since its beginnings.

THOMAS EDISON AND ELECTRIC LIGHTING

Although Thomas Alva Edison is best known for his contributions to the electrical industry, his experimentation went far beyond the light bulb. Edison was quite possibly the greatest inventor of the turn of the century, saying famously that he “hoped to have a minor invention every ten days and a big thing every month or so.” He registered 1,093 patents over his lifetime and ran a world-famous laboratory, Menlo Park, which housed a rotating group of up to twenty-five scientists from around the globe.

Edison became interested in the telegraph industry as a boy, when he worked aboard trains selling candy and newspapers. He soon began tinkering with telegraph technology and, by 1876, had devoted himself full time to lab work as an inventor. He then proceeded to invent a string of items that are still used today: the phonograph, the mimeograph machine, the motion picture projector, the dictaphone, and the storage battery, all using a factory-oriented assembly line process that made the rapid production of inventions possible.

In 1879, Edison invented the item that has led to his greatest fame: the practical incandescent light bulb. He allegedly explored over six thousand different materials for the filament, before stumbling upon carbonized cotton thread as the ideal substance. By 1882, with financial backing largely from financier J. P. Morgan, he had created the Edison Electric Illuminating Company, which began supplying electrical current to a small number of customers in New York City. Morgan guided subsequent mergers of Edison’s other enterprises, including a machine works firm and a lamp company, resulting in the creation of the Edison General Electric Company in 1889.

The next stage of invention in electric power came about with the contribution of George Westinghouse. Westinghouse was responsible for making electric lighting possible on a national scale. While Edison used “direct current” or DC power, which could only extend two miles from the power source, in 1886, Westinghouse invented “alternating current” or AC power, which allowed for delivery over greater distances due to its wavelike patterns. The Westinghouse Electric Company delivered AC power, which meant that factories, homes, and farms—in short, anything that needed power—could be served, regardless of their proximity to the power source. A public relations battle ensued between the Westinghouse and Edison camps, coinciding with the invention of the electric chair as a form of prisoner execution. Edison publicly proclaimed AC power to be best adapted for use in the chair, in the hope that such a smear campaign would result in homeowners becoming reluctant to use AC power in their houses. Although Edison originally fought the use of AC power in other devices, he reluctantly adapted to it as its popularity increased.

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Introducing the Growing Industrial Age

From: Openstax College Textbook on U.S. History

OpenStax’s Timeline of Critical Industrialization Events

The late nineteenth century was an energetic era of inventions and entrepreneurial spirit. Building upon the mid-century Industrial Revolution in Great Britain, as well as answering the increasing call from Americans for efficiency and comfort, the country found itself in the grip of invention fever, with more people working on their big ideas than ever before. In retrospect, harnessing the power of steam and then electricity in the nineteenth century vastly increased the power of man and machine, thus making other advances possible as the century progressed.

Facing an increasingly complex everyday life, Americans sought the means by which to cope with it. Inventions often provided the answers, even as the inventors themselves remained largely unaware of the life-changing nature of their ideas. To understand the scope of this zeal for creation, consider the U.S. Patent Office, which, in 1790—its first decade of existence—recorded only 276 inventions. By 1860, the office had issued a total of 60,000 patents. But between 1860 and 1890, that number exploded to nearly 450,000, with another 235,000 in the last decade of the century. While many of these patents came to naught, some inventions became lynchpins in the rise of big business and the country’s move towards an industrial-based economy, in which the desire for efficiency, comfort, and abundance could be more fully realized by most Americans.

AN EXPLOSION OF INVENTIVE ENERGY

From corrugated rollers that could crack hard, homestead-grown wheat into flour to refrigerated train cars and garment-sewing machines, new inventions fueled industrial growth around the country. As late as 1880, fully one-half of all Americans still lived and worked on farms, whereas fewer than one in seven—mostly men, except for long-established textile factories in which female employees tended to dominate—were employed in factories. However, the development of commercial electricity by the close of the century, to complement the steam engines that already existed in many larger factories, permitted more industries to concentrate in cities, away from the previously essential water power. In turn, newly arrived immigrants sought employment in new urban factories. Immigration, urbanization, and industrialization coincided to transform the face of American society from primarily rural to significantly urban. From 1880 to 1920, the number of industrial workers in the nation quadrupled from 2.5 million to over 10 million, while over the same period urban populations doubled, to reach one-half of the country’s total population.

Advertisements of the late nineteenth century promoted the higher quality and lower prices that people could expect from new inventions. Here, a knitting factory promotes the fact that its machines make seamless hose, while still acknowledging the traditional role of women in the garment industry, from grandmothers who used to sew by hand to young women who now used machines.

In offices, worker productivity benefited from the typewriter, invented in 1867, the cash register, invented in 1879, and the adding machine, invented in 1885. These tools made it easier than ever to keep up with the rapid pace of business growth. Inventions also slowly transformed home life. The vacuum cleaner arrived during this era, as well as the flush toilet. These indoor “water closets” improved public health through the reduction in contamination associated with outhouses and their proximity to water supplies and homes. Tin cans and, later, Clarence Birdseye’s experiments with frozen food, eventually changed how women shopped for, and prepared, food for their families, despite initial health concerns over preserved foods. With the advent of more easily prepared food, women gained valuable time in their daily schedules, a step that partially laid the groundwork for the modern women’s movement. Women who had the means to purchase such items could use their time to seek other employment outside of the home, as well as broaden their knowledge through education and reading. Such a transformation did not occur overnight, as these inventions also increased expectations for women to remain tied to the home and their domestic chores; slowly, the culture of domesticity changed.

Perhaps the most important industrial advancement of the era came in the production of steel. Manufacturers and builders preferred steel to iron, due to its increased strength and durability. After the Civil War, two new processes allowed for the creation of furnaces large enough and hot enough to melt the wrought iron needed to produce large quantities of steel at increasingly cheaper prices. The Bessemer process, named for English inventor Henry Bessemer, and the open-hearth process, changed the way the United States produced steel and, in doing so, led the country into a new industrialized age. As the new material became more available, builders eagerly sought it out, a demand that steel mill owners were happy to supply.

In 1860, the country produced thirteen thousand tons of steel. By 1879, American furnaces were producing over one million tons per year; by 1900, this figure had risen to ten million. Just ten years later, the United States was the top steel producer in the world, at over twenty-four million tons annually. As production increased to match the overwhelming demand, the price of steel dropped by over 80 percent. When quality steel became cheaper and more readily available, other industries relied upon it more heavily as a key to their growth and development, including construction and, later, the automotive industry. As a result, the steel industry rapidly became the cornerstone of the American economy, remaining the primary indicator of industrial growth and stability through the end of World War II.

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Practice Essay #2

Practice: Write 300-600 words arguing for a time when public safety is more important than privacy.

Be sure to write a thesis statement, vary your sentence structures & vocabulary, and proof your final work.

Total word Count : 0 words.
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Practice Essay #1

Practice: Write 300-600 words arguing for a time when public safety is more important than privacy.

Be sure to write a thesis statement, vary your sentence structures & vocabulary, and proof your final work.

You can upload a document with your essay here. (If you use Grammar Check, please take note of the types of changes you made. We can discuss how to do those fixes without relying on Grammar Check.)

Upload your picture here.
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Oxidation-Redox Reactions

From: OpenStax College Chemistry book

Earth’s atmosphere contains about 20% molecular oxygen, O2, a chemically reactive gas that plays an essential role in the metabolism of aerobic organisms and in many environmental processes that shape the world. The term oxidation was originally used to describe chemical reactions involving O2, but its meaning has evolved to refer to a broad and important reaction class known as oxidation-reduction (redox) reactions. A few examples of such reactions will be used to develop a clear picture of this classification.

Some redox reactions involve the transfer of electrons between reactant species to yield ionic products, such as the reaction between sodium and chlorine to yield sodium chloride:

2Na(𝑠)+Cl2(𝑔)⟶2NaCl(𝑠)2Na(s)+Cl2(g)⟶2NaCl(s)

It is helpful to view the process with regard to each individual reactant, that is, to represent the fate of each reactant in the form of an equation called a half-reaction:

2Na(𝑠)⟶2Na+(𝑠)+2e−Cl2(𝑔)+2e−⟶2Cl−(𝑠)2Na(s)⟶2Na+(s)+2e−Cl2(g)+2e−⟶2Cl−(s)

These equations show that Na atoms lose electrons while Cl atoms (in the Cl2 molecule) gain electrons, the “s” subscripts for the resulting ions signifying they are present in the form of a solid ionic compound. For redox reactions of this sort, the loss and gain of electrons define the complementary processes that occur:𝐨𝐱𝐢𝐝𝐚𝐭𝐢𝐨𝐧𝐫𝐞𝐝𝐮𝐜𝐭𝐢𝐨𝐧==loss of electronsgain of electronsoxidation=loss of electronsreduction=gain of electrons

In this reaction, then, sodium is oxidized and chlorine undergoes reduction. Viewed from a more active perspective, sodium functions as a reducing agent (reductant), since it provides electrons to (or reduces) chlorine. Likewise, chlorine functions as an oxidizing agent (oxidant), as it effectively removes electrons from (oxidizes) sodium.𝐫𝐞𝐝𝐮𝐜𝐢𝐧𝐠 𝐚𝐠𝐞𝐧𝐭𝐨𝐱𝐢𝐝𝐢𝐳𝐢𝐧𝐠 𝐚𝐠𝐞𝐧𝐭==species that is oxidizedspecies that is reducedreducing agent=species that is oxidizedoxidizing agent=species that is reduced

Some redox processes, however, do not involve the transfer of electrons. Consider, for example, a reaction similar to the one yielding NaCl:

H2(𝑔)+Cl2(𝑔)⟶2HCl(𝑔)H2(g)+Cl2(g)⟶2HCl(g)

The product of this reaction is a covalent compound, so transfer of electrons in the explicit sense is not involved. To clarify the similarity of this reaction to the previous one and permit an unambiguous definition of redox reactions, a property called oxidation number has been defined. The oxidation number (or oxidation state) of an element in a compound is the charge its atoms would possess if the compound was ionic. The following guidelines are used to assign oxidation numbers to each element in a molecule or ion.

  1. The oxidation number of an atom in an elemental substance is zero.
  2. The oxidation number of a monatomic ion is equal to the ion’s charge.
  3. Oxidation numbers for common nonmetals are usually assigned as follows:
    • Hydrogen: +1 when combined with nonmetals, −1 when combined with metals
    • Oxygen: −2 in most compounds, sometimes −1 (so-called peroxides, O22−),O22−), very rarely −1/2 (so-called superoxides, O2−),O2−), positive values when combined with F (values vary)
    • Halogens: −1 for F always, −1 for other halogens except when combined with oxygen or other halogens (positive oxidation numbers in these cases, varying values)
  4. The sum of oxidation numbers for all atoms in a molecule or polyatomic ion equals the charge on the molecule or ion.

Note: The proper convention for reporting charge is to write the number first, followed by the sign (e.g., 2+), while oxidation number is written with the reversed sequence, sign followed by number (e.g., +2). This convention aims to emphasize the distinction between these two related properties.

EXAMPLE 4.5

Assigning Oxidation NumbersFollow the guidelines in this section of the text to assign oxidation numbers to all the elements in the following species:

(a) H2S

(b) SO32−

(c) Na2SO4

Solution(a) According to guideline 1, the oxidation number for H is +1.

Using this oxidation number and the compound’s formula, guideline 4 may then be used to calculate the oxidation number for sulfur:

charge on H<sub>2</sub>S=0=(2×+1)+(1×x)

x=0−(2×+1)=−2

(b) Guideline 3 suggests the oxidation number for oxygen is −2.

Using this oxidation number and the ion’s formula, guideline 4 may then be used to calculate the oxidation number for sulfur:

charge on SO32− =−2=(3×−2)+(1×𝑥)

𝑥=−2−(3×−2)=+4

(c) For ionic compounds, it’s convenient to assign oxidation numbers for the cation and anion separately.

According to guideline 2, the oxidation number for sodium is +1.

Assuming the usual oxidation number for oxygen (−2 per guideline 3), the oxidation number for sulfur is calculated as directed by guideline 4:

charge on SO42−−=−2=(4×−2)+(1×𝑥)

𝑥=−2−(4×−2)=+6

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Acid-Base Reactions

From: OpenStax College Chemistry book

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to numerous natural and technological processes, ranging from the chemical transformations that take place within cells and the lakes and oceans, to the industrial-scale production of fertilizers, pharmaceuticals, and other substances essential to society. The subject of acid-base chemistry, therefore, is worthy of thorough discussion, and a full chapter is devoted to this topic later in the text.

For purposes of this brief introduction, we will consider only the more common types of acid-base reactions that take place in aqueous solutions. In this context, an acid is a substance that will dissolve in water to yield hydronium ions, H3O+. As an example, consider the equation shown here:

HCl(𝑎𝑞)+H<sub>2</sub>O(𝑎𝑞)⟶Cl−(𝑎𝑞)+H3O<sup>+</sup>(𝑎𝑞)HCl(aq)+H<sub>2</sub>O(aq)⟶Cl−(aq)+H3O<sup>+</sup>(aq)

The process represented by this equation confirms that hydrogen chloride is an acid. When dissolved in water, H3O+ ions are produced by a chemical reaction in which H+ ions are transferred from HCl molecules to H2O molecules.

The nature of HCl is such that its reaction with water as just described is essentially 100% efficient: Virtually every HCl molecule that dissolves in water will undergo this reaction. Acids that completely react in this fashion are called strong acids, and HCl is one among just a handful of common acid compounds that are classified as strong (Table 4.2). A far greater number of compounds behave as weak acids and only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions. Weak acids are commonly encountered in nature, being the substances partly responsible for the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells associated with body odor. A familiar example of a weak acid is acetic acid, the main ingredient in food vinegars:

CH<sub>3</sub>CO<sub>2</sub>H(𝑎𝑞)+H<sub>2</sub>O(𝑙)⇌CH<sub>3</sub>CO<sub>2</sub>−(𝑎𝑞)+H<sub>3</sub>O<sup>+</sup>(𝑎𝑞)CH<sub>3</sub>CO<sub>2</sub>H(aq)+H<sub>2</sub>O(l)⇌CH<sub>3</sub>CO<sub>2</sub><sup>−</sup>(aq)+H<sub>2</sub>O<sup>+</sup>(aq)

When dissolved in water under typical conditions, only about 1% of acetic acid molecules are present in the ionized form, CH3CO2−CH3CO2− (Figure 4.6). (The use of a double-arrow in the equation above denotes the partial reaction aspect of this process, a concept addressed fully in the chapters on chemical equilibrium.)

base is a substance that will dissolve in water to yield hydroxide ions, OH. The most common bases are ionic compounds composed of alkali or alkaline earth metal cations (groups 1 and 2) combined with the hydroxide ion—for example, NaOH and Ca(OH)2. Unlike the acid compounds discussed previously, these compounds do not react chemically with water; instead they dissolve and dissociate, releasing hydroxide ions directly into the solution. For example, KOH and Ba(OH)2 dissolve in water and dissociate completely to produce cations (K+ and Ba2+, respectively) and hydroxide ions, OH. These bases, along with other hydroxides that completely dissociate in water, are considered strong bases.

Consider as an example the dissolution of lye (sodium hydroxide) in water:

NaOH(𝑠)⟶Na<sup>+</sup>(𝑎𝑞)+OH<sup>−</sup>(𝑎𝑞)NaOH(s)⟶Na<sup>+</sup>(aq)+OH<sup>−</sup>(aq)

This equation confirms that sodium hydroxide is a base. When dissolved in water, NaOH dissociates to yield Na+ and OH ions. This is also true for any other ionic compound containing hydroxide ions. Since the dissociation process is essentially complete when ionic compounds dissolve in water under typical conditions, NaOH and other ionic hydroxides are all classified as strong bases.

Unlike ionic hydroxides, some compounds produce hydroxide ions when dissolved by chemically reacting with water molecules. In all cases, these compounds react only partially and so are classified as weak bases. These types of compounds are also abundant in nature and important commodities in various technologies. For example, global production of the weak base ammonia is typically well over 100 metric tons annually, being widely used as an agricultural fertilizer, a raw material for chemical synthesis of other compounds, and an active ingredient in household cleaners (Figure 4.7). When dissolved in water, ammonia reacts partially to yield hydroxide ions, as shown here:

NH<sub>3</sub>(𝑎𝑞)+H2O(𝑙)⇌NH<sub>4</sub><sup>+</sup>(𝑎𝑞)+OH<sup>−</sup>(𝑎𝑞)NH<sub>3</sub>(aq)+H<sub>2</sub>O(l)⇌NH<sub>4</sub><sup>+</sup>(aq)+OH<sup>−</sup>(aq)

This is, by definition, an acid-base reaction, in this case involving the transfer of H+ ions from water molecules to ammonia molecules. Under typical conditions, only about 1% of the dissolved ammonia is present as NH4+NH4+ ions.

EXAMPLE 4.4

Writing Equations for Acid-Base Reactions. Write balanced chemical equations for the acid-base reactions described here:

  • (a) the weak acid hydrogen hypochlorite reacts with water
  • (b) a solution of barium hydroxide is neutralized with a solution of nitric acid

Solution(a) The two reactants are provided, HOCl and H2O. Since the substance is reported to be an acid, its reaction with water will involve the transfer of H+ from HOCl to H2O to generate hydronium ions, H3O+ and hypochlorite ions, OCl.

HOCl(𝑎𝑞)+H<sub>2</sub>O(𝑙)⇌OCl−(𝑎𝑞)+H<sub>3</sub>O<sup>+</sup>

A double-arrow is appropriate in this equation because it indicates the HOCl is a weak acid that has not reacted completely.

(b) The two reactants are provided, Ba(OH)2 and HNO3. Since this is a neutralization reaction, the two products will be water and a salt composed of the cation of the ionic hydroxide (Ba2+) and the anion generated when the acid transfers its hydrogen ion (NO<sub>3</sub><sup>−</sup>).

Ba(OH)<sub>2</sub>(𝑎𝑞)+2HNO<sub>3</sub>(𝑎𝑞)⟶Ba(NO<sub>3</sub>)<sub>2</sub>(𝑎𝑞)+2H<sub>2</sub>O(𝑙)

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Precipitate Reactions

From OpenStax College Chemistry book.

By the end of this section, you will be able to:

  • Define three common types of chemical reactions (precipitation, acid-base, and oxidation-reduction)
  • Classify chemical reactions as one of these three types given appropriate descriptions or chemical equations
  • Identify common acids and bases
  • Predict the solubility of common inorganic compounds by using solubility rules
  • Compute the oxidation states for elements in compounds

Humans interact with one another in various and complex ways, and we classify these interactions according to common patterns of behavior. When two humans exchange information, we say they are communicating. When they exchange blows with their fists or feet, we say they are fighting. Faced with a wide range of varied interactions between chemical substances, scientists have likewise found it convenient (or even necessary) to classify chemical interactions by identifying common patterns of reactivity. This module will provide an introduction to three of the most prevalent types of chemical reactions: precipitation, acid-base, and oxidation-reduction.

Precipitation Reactions and Solubility Rules

precipitation reaction is one in which dissolved substances react to form one (or more) solid products. Many reactions of this type involve the exchange of ions between ionic compounds in aqueous solution and are sometimes referred to as double displacementdouble replacement, or metathesis reactions. These reactions are common in nature and are responsible for the formation of coral reefs in ocean waters and kidney stones in animals. They are used widely in industry for production of a number of commodity and specialty chemicals. Precipitation reactions also play a central role in many chemical analysis techniques, including spot tests used to identify metal ions and gravimetric methods for determining the composition of matter (see the last module of this chapter).

The extent to which a substance may be dissolved in water, or any solvent, is quantitatively expressed as its solubility, defined as the maximum concentration of a substance that can be achieved under specified conditions. Substances with relatively large solubilities are said to be soluble. A substance will precipitate when solution conditions are such that its concentration exceeds its solubility. Substances with relatively low solubilities are said to be insoluble, and these are the substances that readily precipitate from solution. More information on these important concepts is provided in a later chapter on solutions. For purposes of predicting the identities of solids formed by precipitation reactions, one may simply refer to patterns of solubility that have been observed for many ionic compounds.

A vivid example of precipitation is observed when solutions of potassium iodide and lead nitrate are mixed, resulting in the formation of solid lead iodide:

2KI(𝑎𝑞)+Pb(NO3)2(𝑎𝑞)⟶PbI2(𝑠)+2KNO3(𝑎𝑞)2KI(aq)+Pb(NO3)2(aq)⟶PbI2(s)+2KNO3(aq)

This observation is consistent with the solubility guidelines: The only insoluble compound among all those involved is lead iodide, one of the exceptions to the general solubility of iodide salts.

The net ionic equation representing this reaction is:

Pb2+(𝑎𝑞)+2I−(𝑎𝑞)⟶PbI2(𝑠)Pb2+(aq)+2I−(aq)⟶PbI2(s)

Lead iodide is a bright yellow solid that was formerly used as an artist’s pigment known as iodine yellow (Figure 4.4). The properties of pure PbI2 crystals make them useful for fabrication of X-ray and gamma ray detectors.

The solubility guidelines in Table 4.1 may be used to predict whether a precipitation reaction will occur when solutions of soluble ionic compounds are mixed together. One merely needs to identify all the ions present in the solution and then consider if possible cation/anion pairing could result in an insoluble compound. For example, mixing solutions of silver nitrate and sodium fluoride will yield a solution containing Ag+, NO3−,NO3−, Na+, and F ions. Aside from the two ionic compounds originally present in the solutions, AgNO3 and NaF, two additional ionic compounds may be derived from this collection of ions: NaNO3 and AgF. The solubility guidelines indicate all nitrate salts are soluble but that AgF is one of the exceptions to the general solubility of fluoride salts. A precipitation reaction, therefore, is predicted to occur, as described by the following equations:

NaF(𝑎𝑞)+AgNO3(𝑎𝑞)⟶AgF(𝑠)+NaNO3(𝑎𝑞) (molecular)

Ag+(𝑎𝑞)+F−(𝑎𝑞)⟶AgF(𝑠) (net ionic)

EXAMPLE 4.3

Predicting Precipitation ReactionsPredict the result of mixing reasonably concentrated solutions of the following ionic compounds. If precipitation is expected, write a balanced net ionic equation for the reaction.

  • (a) potassium sulfate and barium nitrate
  • (b) lithium chloride and silver acetate
  • (c) lead nitrate and ammonium carbonate

Solution(a) The two possible products for this combination are KNO3 and BaSO4. The solubility guidelines indicate BaSO4 is insoluble, and so a precipitation reaction is expected. The net ionic equation for this reaction, derived in the manner detailed in the previous module, is

Ba2+(𝑎𝑞)+SO2−4(𝑎𝑞)⟶BaSO4(𝑠)Ba2+(aq)+SO42−(aq)⟶BaSO4(s)

(b) The two possible products for this combination are LiC2H3O2 and AgCl. The solubility guidelines indicate AgCl is insoluble, and so a precipitation reaction is expected. The net ionic equation for this reaction, derived in the manner detailed in the previous module, is

Ag+(𝑎𝑞)+Cl−(𝑎𝑞)⟶AgCl(𝑠)Ag+(aq)+Cl−(aq)⟶AgCl(s)

(c) The two possible products for this combination are PbCO3 and NH4NO3. The solubility guidelines indicate PbCO3 is insoluble, and so a precipitation reaction is expected. The net ionic equation for this reaction, derived in the manner detailed in the previous module, is

Pb2+(𝑎𝑞)+CO2−3(𝑎𝑞)⟶PbCO3(𝑠)