Chapter 8: Chemical Equations REVIEW

What four guidelines are useful in balancing an equation?

1. balance the different types of atoms one at the time 2. first balance the atoms of elements that are combined and that appear only once on each side of the equation 3. balance polyatomic ions that appear on both sides of the equation as single units. 4. balance H atoms and O atoms after atoms of all other elements have been balanced

List four observations that indicate that a chemical reaction may be taking place.

1. temperature change 2. production of a gas 3. formation of a precipitant 4. color change

List the three requirements for a correctly written chemical equation.

1. the equation must represent the facts 2. the equation must include symbols and formulas for all elements and compounds used as reactants and formed as products 3. law of the conservation of atoms must be satisfied

what are the four steps in chemical equation writing?

1. write word equations using names of products and reactants 2. substitute the correct formulas for names and write the formula equation 3. balance according to the law of the conservation of atoms 4. count atoms to ensure equation is correctly balanced

How many atoms of each type are represented in the following? 6Al2(SeO4)3

12 atoms Al, 18 atoms Se, 72 atoms O

How many atoms of each type are represented in the following? 4C3H8

12 atoms C, 32 atoms H

How many atoms of each type are represented in the following? 4Mg3(PO4)2

12 atoms Mg, 8 atoms P, 32 atoms O

Balance the following: Al + H2SO4 →Al2(SO4)3 + H2

2 Al + 3 H2SO4 →Al2(SO4)3 + 3 H2

Balance the following: Al + Fe2O3 →Al2O3 + Fe

2 Al + Fe2O3 →Al2O3 + 2 Fe

Balance the following equation: Al(OH)3(s) + H2SO4(aq) → Al2(SO4)3(aq) + H2O(l)

2 Al(OH)3 + 3 H2SO4 → Al2(SO4)3 + 6 H2O

Write the chemical equation that relates to the following word equation. Include symbols for physical states in the equation solid zinc sulfide + oxygen gas → solid zinc oxide + sulfur dioxide gas

2 ZnS (s) + 3 O2 (g) --> 2 ZnO (s) + 2 SO2 (g)

How many atoms of each type are represented in the following? 3Ba(ClO3)2

3 atoms Ba, 6 atoms Cl, 18 atoms O

Complete the following synthesis reaction by writing both word and chemical equation: . sodium + oxygen → _____

4 Na + O2 ---> 2 Na2O

Based on the activity series of metals and halogens, which element within each pair is more likely to replace the other in a compound? Au and Ag

Ag will replace Au

Write formulas for the following compound: carbon tetrachloride

CCl4

Carbon tetrachloride is used as an intermediate chemical in the manufacture of other chemicals. It is prepared in liquid form by reacting chlorine gas with methane gas. Hydrogen chloride gas is also formed in this reaction. Write the balanced chemical equation for the production of carbon tetrachloride

CH4 (g) + 4 Cl2 (g) ---> CCl4 (l) + 4 HCl (g)

Use the activity series to predict whether each of the following synthesis reactions will occur, and write the chemical equations for those predicted to occur: Ca(s) + O2(g) → _____

Ca reacts with oxygen forming oxides, CaO balanced: 2 Ca + O2 ---> 2 CaO

Write and balance the following equation, and then identify by type: calcium chlorate → calcium chloride + oxygen

Ca(ClO3)2 ---> CaCl2 + 3 O2 decomposition of metallic chlorate

Write formulas for the following compound: calcium nitrate

Ca(NO3)2

Balance the following: Ca(OH)2 + (NH4)2SO4 → CaSO4 + NH3 + H2O

Ca(OH)2 + (NH4)2SO4 → CaSO4 + 2 NH3 + 2 H2O

Based on the activity series of metals and halogens, which element within each pair is more likely to replace the other in a compound? Bi and Cr

Cr will replace Bi

Write chemical equations for the following sentence: Iron(III) oxide reacts with carbon monoxide to produce iron and carbon dioxide.

Fe2O3 + 3 CO2 ---> 2 Fe + 3 CO2

Balance the following: H2 + Cl2 → HCl

H2 + Cl2 → 2 HCl

Write and balance the following equation, and then identify by type: hydrogen + iodine → hydrogen iodide

H2 + I2 ---> 2 HI synthesis

What product is missing in the following equation? MgO + 2HCl → MgCl2 + _____

H2O

Based on the activity series of metals and halogens, which element within each pair is more likely to replace the other in a compound? K and Na

K will replace Na

Write formulas for the following compound: potassium hydroxide

KOH

For the following synthesis reaction, identify the missing reactant(s) or product(s), and then balance the resulting equation: Li + Cl2 → _____

LiCl balanced: 2 Li + CL2 ---> 2 LiCl

Complete the following synthesis reaction by writing the chemical equation: magnesium + fluorine → _____

Mg + F2 ---> MgF2

Write and balance the following equation, and then identify by type: magnesium hydroxide → magnesium oxide + water

Mg(OH)2 ---> MgO + H2O decomposition of a metallic hydroxide

Write formulas for the following compound: magnesium bromide

MgBr2

Write formulas for the following compound: sodium carbonate

Na2CO3

For the following synthesis reaction, identify the missing reactant(s) or product(s), and then balance the resulting equation: Mg + _____ → MgO

O2 balanced: Mg + O2 ---> MgO

Write chemical equations for the following sentence: Phosphoric acid,H3PO4,is produced through the reaction between tetraphosphorus decoxide and water.

P4O10 + 6H2O ---> 4 H3PO4

Balance the following: Pb(CH3COO)2 + H2S → PbS + CH3COOH

Pb(CH3COO)2 + H2S → PbS + 2 CH3COOH

Based on the activity series of metals and halogens, which element within each pair is more likely to replace the other in a compound? Fe and Sr

Sr will replace Fe

What is meant by the activity of an element? How does this description differ for metals and nonmetals?

activity is the ability of an element to react, for metals to have greater activity it means they lose electrons more easily forming cations. for nonmetals to have a greater activity it means they gain electrons easier, forming anions

Define the following: aqueous solution

aqueous solution: the reactant or product is dissolved in water

In what environment do many single replacement reactions commonly occur?

aqueous solutions

Complete and balance the following reaction observed to occur, and then identify by type: toluene,C7H8 + oxygen → _____

carbon dioxide and water C7H8 + 9 O2 ---> 7 CO2 + 4 H2O combustion

Complete and balance the following reaction observed to occur, and then identify by type: nonane,C9H20 + oxygen → _____

carbon dioxide and water C9H20 + 14 O2 ---> 9 CO2 + 10 H2O combustion

Define the following: reversible reaction

chemical reaction in which the products reform the original reactants

What is meant by the term coefficient in relation to a chemical equation?

coefficient: small whole number that appears in front of a formula in a chemical equation

Complete and balance the equation for the following combustion reaction: C5H12 + O2 → _____

combustion reaction produces carbon dioxide and water, CO2 + H2O balanced: C5H12 + 8 O2 ---> 5 CO2 + 6 H2O

Complete and balance the equation for the following combustion reaction: CH4 + O2 → _____

combustion reaction produces carbon dioxide and water, CO2 + H2O balanced: CH4 + 2 O2 ---.> CO2 + 2 H2O

The following equation is incorrect in some way. Identify and correct each error, and then balance the equation. MgCO3 → MgO2 + CO2

decomposition of a metallic carbonate always produces metallic oxide and carbon dioxide. MgO2 is magnesium peroxide. balanced: MgCO3 → MgO + CO2

Complete and balance the equation for the following decomposition reaction: H2O (l) --electricity →

decomposition of binary compound breaks into component parts, H2 and O2 balanced: 2 H2O --> 2H2 + O2

Complete and balance the equation for the following decomposition reaction: Ag2O --heat-->

decomposition of metallic oxide produces metal and oxygen, Ag and O2 balanced: 2 Ag2O ---> 4 Ag + O2

The following equation is incorrect in some way. Identify and correct each error, and then balance the equation. NaI + Cl2 → NaCl + I

iodine is a diatomic molecule meaning it cannot exist by itself but must exist in pairs. balanced: 2 NaI + Cl2 → 2 NaCl + I2

What is an activity series of elements?

list of elements organized according to the ease with which the elements undergo certain chemical reactions

Identify the compound that could undergo decomposition to produce the following products, and then balance the final equation: magnesium oxide and water

magnesium hydroxide ---> magnesium oxide + water balanced: Mg(OH)2 ---> MgO + H2O

Complete the following synthesis reactions by writing the product and chemical equation for magnesium + oxygen → _____

magnesium oxide equation: 2 Mg + O2 ---> 2 MgO

In the following combustion reaction, identify the missing reactant(s), product(s), or both, and then balance the resulting equation: C3H8 + _____ → _____ + H2O

missing: oxygen & carbon dioxide, O2 & CO2 balanced: C3H8 + 5O2 ---> 3 CO2 + 4H2O

In the following combustion reaction, identify the missing reactant(s), product(s), or both, and then balance the resulting equation: C2H5OH + _____ → _____ + ____

missing: oxygen, carbon dioxide and water, O2, CO2, H2O balanced: C2H5OH + 3 O2 ---> 2 CO2 + 3 H2O

Identify the compound that could undergo decomposition to produce the following products, and then balance the final equation: nickel chloride and oxygen

nickel chlorate ---> nickel chloride + oxygen balanced: Ni(ClO3)2 ---> NiCl2 + 3 O2

Use the activity series to predict whether each of the following reactions will occur, and write the balanced chemical equations for those predicted to occur: Pb(s) + ZnCl2(s) → _____

no reaction

Use the activity series to predict whether each of the following synthesis reactions will occur, and write the chemical equations for those predicted to occur: Au(s) + O2(g) → _____

no reaction

Complete and balance the equation for the following single-replacement reaction: Al + NiSO4 → _____

products: Al2(SO4)3 + NI balanced: 2 Al + 3 NiSO4 ---> Al2(SO4)3 + 3 NI

Using the activity series, predict whether the possible reaction listed below will occur. For the reactions that will occur, write the products and balance the equation. Ba(s) + H2O(l) → _____

products: Ba(OH)2 + H2 balanced: Ba + 2 H2O ---> Ba(OH)2 + H2

Complete and balance the equation for the following double-replacement reaction: LiOH(aq) + Fe(NO3)3(aq) → _____

products: Fe(OH)3 + LiNO3 balanced: 3 LiOH + Fe(NO3)3 ---> Fe(OH)3 + 3 LiNO3

Using the activity series, predict whether the possible reaction listed below will occur. For the reactions that will occur, write the products and balance the equation. Cl2(g) + KI(aq) → _____

products: KCl + I2 balanced: Cl2 + 2 KI ---> 2 KCl + I2

Complete and balance the equation for the following double-replacement reaction: Mg(NO3)2(aq) + KOH(aq) → _____

products: KNO3 + Mg(OH)2 balanced: Mg(NO3)2 + 2 KOH ---> 2 KNO3 + Mg(OH)2

Complete and balance the equation for the following reaction, and identify the type of reaction it represents: (NH4)2S(aq) + ZnCl2(aq) → _____ + ZnS(s)

products: NH4Cl + ZnS balanced: (NH4)2S + ZnCl2 ---> 2 NH4Cl + ZnS double replacement

Using the activity series, predict whether the possible reaction listed below will occur. For the reactions that will occur, write the products and balance the equation. Ni(s) + CuCl2(aq) → ____

products: NiCl2 + Cu balanced: Ni + CuCl2 ---> NiCl2 + Cu

Translate the following chemical equations into a sentence. CaH2(s) + 2H2O(l) → Ca(OH)2(aq) + 2H2(g)

solid calcium hydride plus liquid water yields aqueous calcium hydroxide and hydrogen gas

Define the following: catalyst

substance that changes the rate of a chemical reaction but can be recovered, unchanged. it does not participate in the chemical reaction

In general, how do single-replacement reactions compare with synthesis and decomposition reactions in terms of the amount of energy involved?

the amount of energy involved in a single displacement reaction is smaller than the amount involved in a synthesis or decomposition reaction

What is the chemical principle upon which the activity series of metals is based?

the ease with which metals lose electrons

What is the basis for the ordering of the elements in the activity series?

the elements are organized according to reactivity determined by a single displacement reaction

What is the significance of the distance between two metals in the activity series?

the further two metals are apart the more likely they are to replace one another

How does the presence of a coefficient affect the number of atoms of each type in the formula that it precedes?

the number of atoms is multiplied by the coefficient

What quantitative information is revealed by a chemical equation?

the number of molecules, moles, and atoms

Complete and balance the equation for the following single-replacement reaction: Na + H2O → _____

the replacement of H in H2O by a metal results in a metallic hydroxide and H2 as the products balanced: 2 Na + 2 H2O ---> 2 NaOH + H2

How are most decomposition reactions initiated?

when energy in the form of electricity or heat is added

Complete and balance the following reaction observed to occur, and then identify by type: zinc + sulfur → _____

zinc sulfide Zn + S ---> ZnS synthesis