in a chemical reaction two gases combine to form a solid. what do you expect for the sign of δs?

Chemical Reactions

Word Equations

• Write word equations that draw chemic reactions.

What's for dinner?

Various ways of recording recipes accept adult over the centuries. The cookbook shown above was written by a woman who probably nerveless all her own recipes. Later, printed cookbooks became available (even guys had no excuse for not being able to cook). Today nosotros can find recipes on a number of internet sites and can speedily search for information on how to cook anything nosotros want. Reading a recipe sometimes requires nosotros empathise a few codes and symbols (what's the difference between a tsp and a Tsp?), but the information on what we start with and what nosotros end up with is there.

Writing Chemical Equations

Chemical reactions are occurring all around you. Plants employ sunlight to drive their photosynthetic process and produce energy. Cars and other vehicles burn down gasoline in order to power their engines. Batteries employ electrochemical reactions to produce energy and power many everyday devices. Many chemical reactions are going on within you equally well, peculiarly during the digestion of food.

In math grade, you take written and solved many mathematical equations. Chemists go along track of chemical reactions by writing equations likewise. In whatsoever chemic reaction one or more substances, chosen reactants , are converted into 1 or more new substances, called products . The general form of the equation for such a procedure looks like this.

Different in a math equation, a chemic equation does not use an equal sign. Instead the pointer is called a yield sign and so the equation is described every bit "reactants yield products".

Word Equations

You lot can draw a chemic reaction by writing a word equation . When silverish metal is exposed to sulfur information technology reacts to form silver sulfide. Silverish sulfide is unremarkably known as tarnish and turns the surface of silverish objects dark and streaky blackness (run across Figure below ). The sulfur that contributes to tarnish can come from traces of sulfur in the air or from food such as eggs. The give-and-take equation for the procedure is:

The silver and the sulfur are the reactants in the equation, while the silver sulfide is the product.

Figure 11.1

The coffee percolator on the left has been tarnished from exposure to sulfur. Tarnish is the chemical compound silver sulfide. The same percolator on the correct has been polished with a tarnish removal product in lodge to restore its silvery finish.

Another common chemical reaction is the burning of marsh gas gas. Methane is the major component of natural gas and is unremarkably burned on a gas stove or in a Bunsen burner ( Figure below ). Burning is a chemic reaction in which some type of fuel is reacted with oxygen gas. The products of the reaction in the called-for of methane likewise as other fuels are carbon dioxide and water. The word equation for this reaction is:

Figure 11.2

A Bunsen burner is commonly used to rut substances in a chemistry lab. Methane is reacted with oxygen to form carbon dioxide and water.

Word equations can be very useful, merely do have i major drawback. They cannot be used for whatsoever quantitative work. A word equation does not tell how many moles of each material are needed or how many moles of product are formed.

Summary

• Word equations are used to describe the conversion of reactants to products.

Practice

Questions

Read the material at the link below and do the exercise problems:

http://www.dynamicscience.com.au/tester/solutions/chemical science/chemical%20equations.htm

Review

Questions

1. Write the generic form of a chemical reaction.
2. What are reactants?
3. What are products?

• chemical reaction : Conversion of reactants to products
• product: The result of chemical reaction
• reactant: The starting material for a chemic reaction
• discussion equation: A description of a chemic reaction using the names of the compounds.

Chemical Equations

• Describe the symbols used in a chemic equation.

How do yous brand Shrimp gumbo?

Shrimp gumbo is one of many enjoyable dishes that are role of the Cajun culture in Louisiana. It's a spicy dish that needs conscientious control of all the ingredients and then that it has a "kicking", but is not overwhelming. Recipes tell not but what is in the preparation, but describes how much of each ingredient and details of how to cook the meal. Similarly, We need this type of information in order to behave out chemic reactions successfully and safely.

Chemic Equations

Word equations are fourth dimension-consuming to write and do not evidence to exist convenient for many of the things that chemists need to do with equations. A chemical equation is a representation of a chemic reaction that displays the reactants and products with chemic formulas. The chemical equation for the reaction of methane with oxygen is shown:

The equation above, called a skeleton equation, is an equation that shows just the formulas of the reactants and products with nothing to point the relative amounts. The first step in writing an accurate chemical equation is to write the skeleton equation, making sure that the formulas of all substances involved are written correctly. All reactants are written to the left of the yield arrow, separated from one another by a plus sign. Likewise, products are written to the correct of the yield arrow, too separated with a plus sign.

It is often of import to know the physical states of the reactants and products taking role in a reaction. To do this, put the appropriate symbol in parentheses after each formula: ( south ) for solid, ( l ) for liquid, ( k ) for gas, and ( aq ) for an aqueous (water-based) solution. The previous reaction becomes:

The Table below shows a list of symbols used in chemical equations. Some, such as the double arrow which represents equilibrium, and the employ of a catalyst in a reaction, volition be treated in detail in other concepts.

Symbols Used in Chemical Equations

Symbol	Description
+	Used to dissever multiple reactants or products
	yield sign; separates reactants from products
	replaces the yield sign for reversible reactions that achieve equilibrium
( s )	reactant or production in the solid state
( 50 )	reactant or product in the liquid state
( g )	reactant or production in the gas state
( aq )	reactant or product in an aqueous solution (dissolved in water)
	formula written higher up the arrow is used as a catalyst in the reaction
	triangle indicates that the reaction is being heated

Summary

Click on the image in a higher place for more than content

http://www.youtube.com/sentinel?v=lSoRj_iBwYc

Review

Questions

1. What does a skeleton equation tell yous?
2. Why would you want to know the physical land of materials?
3. What does the symbol mean?
4. If I encounter over the pointer, what will I practice?

• chemical equation: A representation of a chemic reaction that displays the reactants and products with chemical formulas
• skeleton equation: An equation that shows only the formulas of the reactants and products with goose egg to bespeak the relative amounts.

Balancing Equations

• Residuum chemical equations when given the skeleton information.

Whatever Leftovers?

When you melt a meal, quite often in that location are leftovers considering you prepared more than people would eat at ane sitting. Sometimes when y'all repair a slice of equipment, you end up with what are called "pocket parts", small pieces y'all put in your pocket considering you're not sure where they vest. Chemistry tries to avoid leftovers and pocket parts. In normal chemical processes, we cannot create or destroy thing (constabulary of conservation of mass). If we showtime out with ten carbon atoms, we demand to end up with ten carbon atoms. John Dalton' atomic theory said that chemical reactions basically involve the rearrangement of atoms. Chemical equations demand to follow these principles in society to be correct.

Balancing Chemical Equations

A balanced equation is a chemic equation in which mass is conserved and in that location are equal numbers of atoms of each element on both sides of the equation. We can write a chemical equation for the reaction of carbon with hydrogen gas to course marsh gas (CH _iv ).

In order to write a correct equation, you lot must offset write the correct skeleton equation with the right chemical formulas. Recall that hydrogen is a diatomic molecule then is written equally H ₂ .

When we count the number of atoms of both elements, shown under the equation, nosotros see that the equation is non balanced. There are only 2 atoms of hydrogen on the reactant side of the equation, while there are 4 atoms of hydrogen on the production side. Nosotros tin can balance the higher up equation by adding a coefficient of 2 in forepart of the formula for hydrogen.

A coefficient is a modest whole number placed in front of a formula in an equation in order to balance it. The two in forepart of the H ₂ ways that at that place are a total of atoms of hydrogen equally reactants. Visually, the reaction looks like the Figure below .

Figure 11.3

Reaction betwixt carbon and hydrogen to form methyl hydride.

In the counterbalanced equation, there is one atom of carbon and iv atoms of hydrogen on both sides of the arrow. Below are guidelines for writing and balancing chemic equations.

1. Determine the correct chemical formulas for each reactant and product.
2. Write the skeleton equation.
3. Count the number of atoms of each element that appears as a reactant and every bit a product. If a polyatomic ion is unchanged on both sides of the equation, count it as a unit of measurement.
4. Residual each chemical element on at a time past placing coefficients in front of the formulas. No coefficient is written for a one. It is best to begin past balancing elements that only appear in ane formula on each side of the equation. NEVER modify the subscripts in a chemical formula – you lot can merely balance equations by using coefficients.
5. Check each cantlet or polyatomic ion to be sure that they are equal on both sides of the equation.
6. Make sure that all coefficients are in the lowest possible ratio. If necessary, reduce to the lowest ratio.

Sample Problem: Balancing Chemical Equations

Aqueous solutions of pb(2) nitrate and sodium chloride are mixed. The products of the reaction are an aqueous solution of sodium nitrate and a solid precipitate of lead(2) chloride.

Step 1: Programme the trouble.

Follow the steps for writing and balancing a chemical equation.

Footstep two: Solve.

Write the skeleton equation with the correct formulas.

Count the number of each atom or polyatomic ion on both sides of the equation.

reactants	products
1 Lead atom	1 Pb atom
2 NO three – ions	1 NO 3 – ions
i Na atom	1 Na atom
1 Cl atom	2 Cl atoms

The nitrate ions and the chlorine atoms are unbalanced. Start past placing a 2 in front end of the NaCl. This increases the reactant counts to 2 Na atoms and 2 Cl atoms. Then place a 2 in forepart of the NaNO _iii . The consequence is:

The new count for each atom and polyatomic ion becomes:

reactants	products
1 Pb atom	1 Pb atom
2 NO iii – ions	ii NO iii – ions
2 Na cantlet	two Na cantlet
2 Cl atoms	two Cl atoms

Step 3: Recollect about your upshot.

The equation is at present balanced since there are equal numbers of atoms of each element on both sides of the equation.

Summary

• The process of balancing chemical equations is described.

Practice

Questions

Go some experience in balancing chemical equations at the post-obit spider web site:

http://www.sciencegeek.net/APchemistry/APtaters/EquationBalancing.htm

Review

Questions

1. What is the law of conservation of mass?
2. How did Dalton describe he profess of a chemical reaction?
3. Why don't we change the subscripts in order to residue an equation?

• balanced equation: A chemical equation in which mass is conserved and there are equal numbers of atoms of each element on both sides of the equation.
• coefficient: A small whole number placed in front of a formula in an equation in social club to residual it.

Combination Reactions

• Define combination reaction.
• Write products of combination reactions when given the reactants.

How useful is a wheel rim?

A wheel rim is not very useful by itself. Driving on the rim can damage it and make for a very rough ride. When the rim is combined with a tire, the product tin be put on a car and used for a condom and comfortable ride. The ii dissever items accept combined to make something that improves the motorcar ride.

Combination Reactions

A combination reaction is a reaction in which two or more than substances combine to class a single new substance. Combination reactions tin can also be called synthesis reactions. The general form of a combination reaction is:

One combination reaction is two elements combining to grade a compound. Solid sodium metal reacts with chlorine gas to produce solid sodium chloride.

Detect that in order to write and remainder the equation correctly, information technology is of import to remember the 7 elements that be in nature every bit diatomic molecules (H ₂ , Northward ₂ , O ₂ , F ₂ , Cl ₂ , Br ₂ , and I ₂ ).

One sort of combination reaction that occurs oftentimes is the reaction of an element with oxygen to form an oxide. Metals and nonmetals both react readily with oxygen under near conditions. Magnesium reacts rapidly and dramatically when ignited, combining with oxygen from the air to produce a fine powder of magnesium oxide.

This reaction can exist seen in the following video: http://www.youtube.com/watch?five=NnFzHt6l4z8 (0:37).

Click on the image higher up for more than content

Sulfur reacts with oxygen to form sulfur dioxide.

When nonmetals react with one another, the production is a molecular chemical compound. Ofttimes, the nonmetal reactants tin can combine in different ratios and produce different products. Sulfur tin can also combine with oxygen to produce sulfur trioxide.

Transition metals are capable of adopting multiple positive charges inside their ionic compounds. Therefore, nigh transition metals are capable of forming different products in a combination reaction. Atomic number 26 reacts with oxygen to course both iron(II) oxide and atomic number 26(III) oxide.

Sample Trouble: Combination Reactions

Potassium is a very reactive alkali metallic that must exist stored under oil in lodge to prevent it from reacting with air. Write the balanced chemical equation for the combination reaction of potassium with oxygen.

Stride 1: Plan the problem

Make sure formulas of all reactants and products are right before balancing the equation. Oxygen gas is a diatomic molecule. Potassium oxide is an ionic compound and and then its formula is synthetic by the crisscross method. Potassium as an ion becomes 1000 ⁺ , while the oxide ion is O ²⁻ .

Footstep 2: Solve

The skeleton (unbalanced) equation:

The equation is then easily counterbalanced with coefficients.

Footstep 3: Think about your result

Formulas are correct and the resulting combination reaction is counterbalanced.

Combination reactions can also have place when an element reacts with a chemical compound to form a new compound composed of a larger number of atoms. Carbon monoxide reacts with oxygen to form carbon dioxide according to the equation:

Two compounds may also react to from a more complex compound. A very common example is the reactions of oxides with water. Calcium oxide reacts readily with water to produce an aqueous solution of calcium hydroxide.

Sulfur trioxide gas reacts with water to form sulfuric acid. This is an unfortunately common reaction that occurs in the atmosphere in some places where oxides of sulfur are present as pollutants. The acid formed in the reaction falls to the basis equally acid rain.

Figure eleven.four

Acid rain has severe consequences on both natural and human-made objects. Acid rain degrades marble statues similar the ane on the left (A). The trees in the forest on the right (B) have been killed by acrid rain.

Summary

• Combination reactions occur when two or more substances combine to class a new substance.

Practice

Questions

Complete the reactions and rest the equations on the worksheet at the link below:

http://www.sciencegeek.net/Chemical science/chempdfs/EquationsWorksheet2.pdf

Review

Questions

1. What are combination reactions?
2. Write the product of the following reaction:
3. Is a combination reaction? Explicate your answer.

• combination reaction: A reaction in which 2 or more than substances combine to form a single new substance.

Decomposition Reactions

• Define decomposition reaction.
• Write the products of decomposition reactions when given the reactant.
• Write the reactant of a decomposition reaction when given the products.

How does a decomposition reaction work?

Antoine Lavoisier is widely known as the "father of modern chemical science". He was one of the showtime to study chemic reactions in detail. Lavoisier reacted mercury with oxygen to course mercuric oxide equally part of his studies on the limerick of the atmosphere. He was then able to show that the decomposition of mercuric oxide produced mercury and oxygen. The diagram in a higher place shows the appliance used by Lavoisier to study the formation and decomposition of mercuric oxide.

Decomposition Reactions

A decomposition reaction is a reaction in which a compound breaks downwards into two or more simpler substances. The full general form of a decomposition reaction is:

Nigh decomposition reactions crave an input of energy in the form of heat, light, or electricity.

Binary compounds are compounds composed of simply two elements. The simplest kind of decomposition reaction is when a binary compound decomposes into its elements. Mercury(Two) oxide, a ruby solid, decomposes when heated to produce mercury and oxygen gas.

Figure 11.5

Mercury(2) oxide is a red solid. When it is heated, it decomposes into mercury metal and oxygen gas.

A reaction is also considered to exist a decomposition reaction even when one or more of the products are still compounds. A metal carbonate decomposes into a metallic oxide and carbon dioxide gas. For example, calcium carbonate decomposes into calcium oxide and carbon dioxide.

Metallic hydroxides decompose on heating to yield metal oxides and water. Sodium hydroxide decomposes to produce sodium oxide and water.

Some unstable acids decompose to produce nonmetal oxides and h2o. Carbonic acid decomposes hands at room temperature into carbon dioxide and h2o.

Sample Problem: Decomposition Reactions

When an electric electric current is passed through pure h2o, it decomposes into its elements. Write a balanced equation for the decomposition of water.

Step 1: Plan the problem

Water is a binary chemical compound composed of hydrogen and oxygen. The hydrogen and oxygen gases produced in the reaction are both diatomic molecules.

Step two: Solve

The skeleton (unbalanced) equation:

Note the abbreviation "elec" above the pointer to indicate the passage of an electric current to initiate the reaction. Balance the equation.

Step 3: Recollect about your result

The products are elements and the equation is balanced.

Summary

• A definition of decomposition reaction and example reactions are given.

Practice

Questions

Write the reactions (including names and counterbalanced equations) equally requested on the following web site:

http://www.sciencegeek.net/Chemistry/chempdfs/EquationsWorksheet3.pdf

Review

Questions

1. What is a decomposition reaction?
2. What is usually needed for a decomposition reaction to take place?
3. Are elements always the product of a decomposition reaction?

• decomposition reaction: A reaction in which a compound breaks down into two or more simpler substances.

Combustion Reaction

• Define combustion reaction.
• Write the products of combustion reactions when given the starting materials.

How do you cook the perfect marshmallow?

Roasting marshmallows over an open up fire is a favorite past-time for campers, outdoor cook-outs, and merely gathering around a fire in the back thousand. The trick is to get the marshmallow a nice aureate brown without catching information technology on fire. Likewise often we are not successful and we see the marshmallow burning on the stick – a combustion reaction taking identify right in front end of us.

Combustion Reactions

A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O ₂ equally one reactant. The combustion of hydrogen gas produces h2o vapor.

Notice that this reaction also qualifies as a combination reaction.

Figure 11.6

Explosion of the Hindenberg.

The Hindenburg was a hydrogen-filled balloon that suffered an accident upon its attempted landing in New Jersey in 1937. The hydrogen immediately combusted in a huge fireball, destroying the airship and killing 36 people. The chemical reaction was a simple one: hydrogen combining with oxygen to produce water.

Many combustion reactions occur with a hydrocarbon, a chemical compound made up solely of carbon and hydrogen. The products of the combustion of hydrocarbons are carbon dioxide and water. Many hydrocarbons are used equally fuel because their combustion releases very large amounts of heat free energy. Propane (C _three H ₈ ) is a gaseous hydrocarbon that is commonly used every bit the fuel source in gas grills.

Exercise Trouble: Combustion Reactions

Ethanol tin exist used as a fuel source in an alcohol lamp. The formula for ethanol is C ₂ H ₅ OH. Write the balanced equation for the combustion of ethanol.

Step 1: Plan the problem

Ethanol and oxygen are the reactants. Equally with a hydrocarbon, the products of the combustion of an alcohol are carbon dioxide and water.

Step ii: Solve

Write the skeleton equation:

Balance the equation.

Step 3: Think nearly your result

Combustion reactions must have oxygen equally a reactant. Note that the water that is produced is in the gas rather than the liquid country considering of the high temperatures that accompany a combustion reaction.

Summary

• Combustion reaction is defined and examples are given.

Practice

Questions

Write the reactions and balance the equations for the questions on the canvas institute on this web site:

http://www.sciencegeek.net/Chemical science/chempdfs/EquationsWorksheet6.pdf

Review

Questions

1. What is needed for a combustion reaction to take identify?
2. What is formed in any combustion reaction?
3. Mercury reacts with oxygen to grade mercuric oxide. Is this a combustion reaction?
4. What are the products of whatever combustion reaction involving a hydrocarbon?

• combustion reaction: A reaction in which a substance reactants with oxygen gas, releasing energy in the form of light and oestrus.

Single-Replacement Reactions

• Define single-replacement reaction.
• Requite examples of single-displacement reactions.

Why is the silver dark?

The cup shown above provides an example of tarnish, a chemic reaction acquired when silver metal reacts with hydrogen sulfide gas produced by some industrial processes or every bit a result of decaying animal or plant materials:

The tarnish can exist removed using a number of polishes, but the process also removes a small amount of silver along with the tarnish.

Single-Replacement Reactions

A single-replacement reaction is a reaction in which ane element replaces a similar chemical element in a compound. The general form of a single-replacement (also chosen single-displacement) reaction is:

In this general reaction, element is a metallic and replaces element , also a metal, in the compound. When the chemical element that is doing the replacing is a nonmetal, it must supervene upon some other nonmetal in a chemical compound, and the general equation becomes:

is a nonmetal and replaces the nonmetal in the compound with .

Metal Replacement

Magnesium is a more reactive metallic than copper. When a strip of magnesium metal is placed in an aqueous solution of copper(Ii) nitrate, information technology replaces the copper. The products of the reaction are aqueous magnesium nitrate and solid copper metal.

This subcategory of single-replacement reactions is called a metal replacement reaction because it is a metal that is being replaced (zinc).

Hydrogen Replacement

Many metals react hands with acids and when they do then, one of the products of the reaction is hydrogen gas. Zinc reacts with muriatic acid to produce aqueous zinc chloride and hydrogen ( Figure below ).

In a hydrogen replacement reaction, the hydrogen in the acid is replaced by an active metal.

Figure 11.7

Zinc metal reacts with hydrochloric acid to give off hydrogen gas in a single-deportation reaction.

Some metals are so reactive that they are capable of replacing the hydrogen in water. The products of such a reaction are the metallic hydroxide and hydrogen gas. All group 1 metals undergo this type of reaction. Sodium reacts vigorously with water to produce aqueous sodium hydroxide and hydrogen (see Effigy below ).

Figure xi.viii

Sodium metal reacts vigorously with water, giving off hydrogen gas. A large slice of sodium will often generate and so much heat that the hydrogen will ignite.

Halogen Replacement

The chemical element chlorine reacts with an aqueous solution of sodium bromide to produce aqueous sodium chloride and elemental bromine.

The reactivity of the halogen group (group 17) decreases from elevation to bottom within the grouping. Fluorine is the most reactive halogen, while iodine is the to the lowest degree. Since chlorine is above bromine, it is more than reactive than bromine and can supervene upon it in a element of group vii replacement reaction.

Summary

• The activity serial describes the relative reactivities of metals and halogens.

Exercise

Questions

Read the material at the link below and practise the practice problems:

http://world wide web.chemteam.info/Equations/SingleReplacement.html

Review

Questions

1. What is a metal replacement reaction?
2. Will a non-metallic replace a metal?
3. What is the most reactive halogen?
4. What products volition I get if I add together potassium metal to h2o?

• single-replacement reaction: A reaction in which one element replaces a similar chemical element in a compound.

Activeness Serial

• Define activity series.
• Use the activity series to predict the issue of reactions.

What's the divergence between the two pictures above?

We meet above 2 metals that tin be exposed to water. The picture on the left is of sodium, which gives a violent reaction when information technology comes in contact with water. The film on the right is of silver, a metal and so unreactive with h2o that it can be made into drinking vessels. Both metals accept a single s electron in their outer shell, so you would predict similar reactivities. However, we have a better tool that allows us to make better prediction nearly what will react with what.

The Activity Series

Unmarried-replacement reactions only occur when the chemical element that is doing the replacing is more reactive than the chemical element that is being replaced. Therefore, information technology is useful to have a list of elements in social club of their relative reactivities. The activity series is a list of elements in decreasing society of their reactivity. Since metals supplant other metals, while nonmetals supersede other nonmetals, they each have a separate action serial. The Table below is an activity series of most common metals and of the halogens.

Activity Serial

Activity of Metals	Activity of Halogens
Li K       React with cold water, replacing Ba     hydrogen. Sr Ca Na	F ii Cl 2 Br 2 I 2
Mg Al      React with steam, just non common cold Zn     water, replacing hydrogen. Cr Atomic number 26 Cd
Co Ni     Do non react with water. React Sn    with acids, replacing hydrogen. Pb
H 2
Cu Hg    Unreactive with water or acids. Ag Pt Au

For a single-replacement reaction, a given element is capable of replacing an element that is below it in the action serial. This can exist used to predict if a reaction will occur. Suppose that pocket-size pieces of the metal nickel were placed into ii separate aqueous solutions: one of fe(III) nitrate and ane of lead(Ii) nitrate. Looking at the activeness series, we see that nickel is below fe, but above lead. Therefore, the nickel metal will be capable of replacing the atomic number 82 in a reaction, but volition not exist capable of replacing fe.

In the descriptions that back-trail the activity serial of metals, a given metal is too capable of undergoing the reactions described beneath that section. For example, lithium will react with cold water, replacing hydrogen. It will also react with steam and with acids, since that requires a lower degree of reactivity.

Sample Trouble: Single-Replacement Reactions

Use the activeness series to predict if the post-obit reactions volition occur. If non, write NR. If the reaction does occur, write the products of the reaction and balance the equation.

A.

B.

Footstep 1: Plan the problem

For A, compare the placements of aluminum and zinc on the activeness series. For B, compare the placements of argent and hydrogen.

Stride two: Solve

Since aluminum is in a higher place zinc, information technology is capable of replacing information technology and a reaction will occur. The products of the reaction will exist aqueous aluminum nitrate and solid zinc. Take care to write the correct formulas for the products before balancing the equation. Aluminum adopts a iii+ charge in an ionic compound, so the formula for aluminum nitrate is Al(NO _iii ) ₃ . The counterbalanced equation is:

Since silver is below hydrogen, it is non capable of replacing hydrogen in a reaction with an acrid.

Summary

• Metals and halogens are ranked according to their ability to displacement other metals or halogens below them in the series.

Do

Questions

Take the quiz on the spider web site below:

http://world wide web.sophia.org/chemic-reactions-activity-series-concept

Review

Questions

1. What does the activity series tell united states of america?
2. Can a metal undergo whatsoever of the reactions listed below it in the series?
3. List two metals that cobalt will displace and two that will readapt it.

• action serial: A list of elements in decreasing society of their reactivity.

Double-Replacement Reactions

• Define double-replacement reaction.
• Predict products of double-replacement reactions when given the reactants.

Wanna trade?

The practice of castling (trading one thing for another) has been in beingness from the beginning of time. In the analogy to a higher place, Items like chickens were bartered for newspapers. You lot have something I want, and I have something yous desire. So nosotros trade and we each have something new. Some chemical reactions are like that. Compounds swap parts and you have new materials.

Double-Replacement Reactions

A double-replacement reaction is a reaction in which the positive and negative ions of two ionic compounds exchange places to form two new compounds. The general form of a double-replacement (also chosen double-displacement) reaction is:

In this reaction, and are positively-charged cations, while and are negatively-charged anions. Double-replacement reactions generally occur between substances in aqueous solution. In order for a reaction to occur, one of the products is normally a solid precipitate, a gas, or a molecular compound such as water.

Formation of a Precipitate

A precipitate forms in a double-replacement reaction when the cations from 1 of the reactants combine with the anions from the other reactant to grade an insoluble ionic chemical compound. When aqueous solutions of potassium iodide and lead(2) nitrate are mixed, the following reaction occurs.

There are very stiff attractive forces that occur between Pb ²⁺ and I ⁻ ions and the result is a brilliant xanthous precipitate (run across Figure below ). The other production of the reaction, potassium nitrate, remains soluble.

Figure 11.nine

Formation of lead iodide precipitate.

Formation of a Gas

Some double-replacement reactions produce a gaseous product which then bubbles out of the solution and escapes into the air. When solutions of sodium sulfide and hydrochloric acid are mixed, the products of the reaction are aqueous sodium chloride and hydrogen sulfide gas.

Formation of a Molecular Compound

Another kind of double-replacement reaction is one that produces a molecular chemical compound as i of its products. Many examples in this category are reactions that produce h2o. When aqueous muriatic acid is reacted with aqueous sodium hydroxide, the products are aqueous sodium chloride and h2o.

Sample Problem: Double-Replacement Reactions

Write a complete and balanced chemical equation for the following double-replacement reactions. Ane production is indicated as a guide.

A. (hydrogen cyanide gas is formed)

B. (a precipitate of barium sulfate forms)

Step 1: Plan the trouble

In A, the production of a gas drives the reaction. In B, the product of a precipitate drives the reaction. In both cases, use the ionic charges of both reactants to construct the correct formulas of the products.

Pace 2: Solve

A. The cations of both reactants are +one charged ions, while the anions are -1 charged ions. Subsequently exchanging partners, the balanced equation is:

B. Ammonium ion and nitrate ion are 1+ and i− respectively, while barium and sulfate are 2+ and two−. This must exist taken into account when exchanging partners and writing the new formulas. Then, the equation is counterbalanced.

Step 3: Think near your result

Both are double-replacement reactions. All formulas are correct and the equations are balanced. Occasionally, a reaction volition produce both a gas and a molecular compound. The reaction of a sodium carbonate solution with hydrochloric acid produces aqueous sodium chloride, carbon dioxide gas, and h2o.

Summary

• The double-replacement reaction is described.
• Examples of the double-replacement reaction are shown.

Practise

Questions

Read the material at the web site below and do the practice problems:

http://world wide web.chemteam.info/Equations/DoubleReplacement.html

Review

Questions

1. What are the usual reactants in a double-replacement reaction?
2. List the three possible types of products.
3. Why would you not expect two ionic products?

• double-replacement reaction: A reaction in which the positive and negative ions of two ionic compounds exchange places to course two new compounds.

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Source: https://courses.lumenlearning.com/cheminter/chapter/chemical-reactions/

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