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