Directions:

SHOW ALL WORK in the space provided or your answer is VOID! 

1.  How many formula units are there in 2.5 moles of MgCl₂?

A)  2.5    B)  7.5    C)  1.5 x 10²⁴    D)  4.5 x 10²⁴    E)  4.2 x 10^-24

2.  How many chloride ions are present in 0.100 mol of MgCl₂?

A)0.200 Cl^- ions    D)3.32 x 10^-25 Cl^- ions

B)6.02 x 10²² Cl^- ions E)3.01 x 10²⁴ Cl^- ions

C)1.20 x 10²³ Cl^- ions

3.  How many nitrate ions are present in 0.200 mol of Zn(NO₃)₂?

A)1.20 x 10²³ NO₃^- ions    D)6.64 x 10^-25 NO₃^- ions

B)2.41 x 10²³ NO₃^- ions    E)0.400 NO₃^- ions

C)3.01 x 10²⁴ NO₃^- ions

4.  Consider the following chemical equations.  Select the equations that represent chemical reactions, rather than physical changes.

I. CH₄(g) + O₂(g) → CO₂(g) + H₂O(g)

II.  C₂H₅OH(l) → C₂H₅OH(g)

III.  NaOH(s) → Na⁺(aq) + OH¯(aq)

A)I, II, and IIID)II and III only

B)I and II onlyE)I only

C)I and III only

5.  Calculate the molar mass of CuSO₄·5H₂O.

A)159.62 g/mol     D)185.72 g/mol

B)249.70 g/mol     E)446.48 g/mol

C)177.64 g/mol

6.  If 4.05 x 10²³ molecules of a substance have a mass of 86.2 g, what is the molar mass of the substance?

A)128 g/mol    D)4.70 x 10²¹ g/mol

B)3.49 x 10²⁵ g/mol     E)58.0 g/mol

C)2.13 x 10²² g/mol

7.  Consider the following chemical equations.  Select the equations that represent chemical reactions, rather than physical changes.

I. 2NO(g) + O₂(g) → 2NO₂(g)

II.  CO₂(s) → CO₂(g)

III.  Pb(NO₃)₂(aq) + 2AgCl(aq) → PbCl₂(s) + 2AgNO₃(aq)

A)I, II, and IIID)II and III only

B)I and II onlyE)I only

C)I and III only

8.  Write a complete, balanced equation for the reaction that occurs when sodium metal reacts with water to form hydrogen gas and aqueous sodium hydroxide.

A)Na(s) + H₂O(l) → NaOH(aq) + H(g)

B)Na(s) + H₂O(l) → NaOH(aq) + H₂(g)

C)Na(s) + 2H₂O(l) → NaOH(aq) + 2H₂(g)

D)Na(s) + 2H₂O(l) → 2NaOH(aq) + 2H₂(g)

E)2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

9.  Zinc metal will react with aqueous hydrochloric acid to produce aqueous zinc chloride and hydrogen gas.  Write a complete, balanced equation for this reaction.

A)Zn(s) + HCl(aq) → ZnCl(aq) + H(g)

B)Zn(s) + HCl(aq) → ZnCl(aq) + H₂(g)

C)Zn(s) + 2HCl(aq) → ZnCl(aq) + H₂(g)

D)Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)

E)2Zn(s) + 2HCl(aq) → 2ZnCl(aq) + H₂(g)

10.  Calculate the number of moles of NaHCO₃ (sodium bicarbonate, or baking soda) in a 5.0 g sample of this substance.

A)0.096 mole   D)3.6 x 10²² moles

B)0.060 mole   E)2.8 x 10²³ mole

C)420 moles

11.  Calculate the number of moles of NaOH (sodium hydroxide, an ingredient in drain cleaners and oven cleaners) in a 10.0 g sample of this substance.

A)1.51 x 10²³ moles    D)4.00 x 10² moles

B)1.66 x 10²³ moleE)0.250 mole

C)0.208 mole

12.  Calculate the number of moles of CaCO₃ (calcium carbonate, or limestone) in a 20.0 g sample of this substance.

A)2.00 x 10³ molesD)1.36 x 10³ moles

B)0.200 mole   E)1.20 x 10³ moles

C)0.294 mole

13.  When solid ammonium carbonate is heated, it decomposes to form ammonia gas, carbon dioxide gas, and water vapor, so that the solid completely disappears.  Write a complete, balanced equation for this reaction.

A)NH₄CO₃(s) → NH₃(g) + CO₂(g) + H₂O(g)

B)NH₄CO₃(s) → NH₂(g) + CO₂(g) + H₂O(g)

C)(NH₄)₂CO₃(s) → NH₃(g) + CO₂(g) + H₂O(g)

D)(NH₄)₂CO₃(s) → NH₃(g) + CO₂(g) + 3H₂O(g)

E)(NH₄)₂CO₃(s) → 2NH₃(g) + CO₂(g) + H₂O(g)

14.  Balance the following skeletal equation:  C₂H₅OH(l) + O₂(g) → CO₂(g) + H₂O(g).

A)C₂H₅OH(l) + O₂(g) → CO₂(g) + 3H₂O(g)

B)C₂H₅OH(l) + O₂(g) → 2CO₂(g) + 3H₂O(g)

C)C₂H₅OH(l) + 2O₂(g) → 2CO₂(g) + 3H₂O(g)

D)C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(g)

E)2C₂H₅OH(l) + 3O₂(g) → 4CO₂(g) + 3H₂O(g)

15.  Balance the following skeletal equation:  NH₃(g) + O₂(g) → NO₂(g) + H₂O(g).

A)4NH₃(g) + 7O₂(g) → 4NO₂(g) + 6H₂O(g)

B)2NH₃(g) + 2O₂(g) → 2NO₂(g) + 3H₂O(g)

C)2NH₃(g) + O₂(g) → NO₂(g) + 2H₂O(g)

D)NH₃(g) + O₂(g) → NO₂(g) + 2H₂O(g)

E)NH₃(g) + O₂(g) → NO₂(g) + H₂O(g)

16.  Balance the following skeletal equation:

Ba(NO₃)₂(aq) + K₂SO₄(aq) → BaSO₄(s) + KNO₃(aq)

A)Ba(NO₃)₂(aq) + K₂SO₄(aq) → BaSO₄(s) + KNO₃(aq)

B)2Ba(NO₃)₂(aq) + K₂SO₄(aq) → 2BaSO₄(s) + KNO₃(aq)

C)2Ba(NO₃)₂(aq) + 2K₂SO₄(aq) → 2BaSO₄(s) + 2KNO₃(aq)

D)2Ba(NO₃)₂(aq) + 2K₂SO₄(aq) → 2BaSO₄(s) + 3KNO₃(aq)

E)Ba(NO₃)₂(aq) + K₂SO₄(aq) → BaSO₄(s) + 2KNO₃(aq)

17.  After the following equation is properly balanced, what is the coefficient in front of O₂?   

S₈(s)   +   O₂(g)   →    SO₃(g)

A)  2    B)  3    C)  8    D)  12    E)  16

18.  A reaction which has two elements as reactants and one compound as a product is:

A)a decomposition reaction.   D)a double-displacement reaction.

B)a combination reaction. E)a combustion reaction.

C)a single-displacement reaction.

19.  A solution of silver nitrate is mixed with a solution of sodium chloride, resulting in a precipitate of silver chloride and a solution of sodium nitrate.  The class of this reaction is:

A)decomposition reaction.D)double-displacement reaction.

B)combination reaction.    E)combustion reaction.

C)single-displacement reaction.

20.  A piece of magnesium metal is placed in a solution of hydrochloric acid, resulting in the formation of hydrogen gas and a solution of magnesium chloride.  The class of this reaction is:

A)decomposition reaction.D)double-displacement reaction.

B)combination reaction.    E)combustion reaction.

C)single-displacement reaction.

21.  The class of the reaction shown in the figure is:

A)decomposition reaction.D)double-displacement reaction.

B)combination reaction.    E)combustion reaction.

C)single-displacement reaction.

22.  Write and balance the equation for the decomposition reaction that occurs when Mercury(II) oxide decomposes to its elements.

A)2HgO(s)  →  2Hg(l)  + O₂(g)    D)HgO₂(s)  →  Hg(l)  + 2O(g)

B)Hg₂O(s)  →  2Hg(l)  + O₂(g)     E)2Hg(l)  +O₂(g) → HgO₂(s)

C)HgO(s)  →  Hg(l)  + O₂(g)

23.  When writing a net ionic equation, how would Mg(NO₃)₂(aq) be represented?

A)Mg²⁺(aq)  +  2NO₃^-(aq)D)Mg(aq)  +  N₂(aq)  + 3O₂(aq)

B)Mg²⁺(aq)  +  NO₃^-(aq)  E)Mg²⁺(aq)  +  2N^3-(aq) + 6O^2-(aq)

C)Mg²⁺(aq)  +  (NO₃)₂^-(aq)

24.  Write and balance a net ionic equation for the reaction between hydrochloric acid and potassium hydroxide.

A)HCl(aq) + KOH(aq)  → KCl(aq) + H₂O(l)

B)H⁺(aq) + O²¯(aq) → OH¯(aq)

C)H⁺(aq) + OH¯(aq) → H₂O(l)

D)Cl¯(aq) + OH⁺(aq) → OHCl(aq)

E)K⁺(aq) + Cl¯(aq) → KCl(aq)

25.  Write and balance a net ionic equation for the reaction between iron(II) chloride and potassium hydroxide to form iron(II) hydroxide and potassium chloride.

A)Fe₂Cl(aq) + OH¯(aq) → FeOH(s) + Cl¯(aq)

B)Fe²⁺(aq) + OH¯(aq) → FeOH(s)

C)Fe²⁺(aq) + 2OH¯(aq) → Fe(OH)₂(s)

D)2Cl¯(aq) + 2K⁺(aq) → 2KCl(s)

E)2Cl¯(aq) + 2K⁺(aq) → 2K(s) + Cl₂(g)

26.  When potassium metal is placed in water, will a reaction occur?  If so, what is the balanced equation for the reaction?

A)No reaction will occur.

B)Yes.  2K(s) + 2H₂O(l) → 2K(OH)₂(aq) + H₂(g)

C)Yes.  2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)

D)Yes.  2K(s) + 2H₂O(l) → 2KH₂O(aq)

E)Yes.  2K(s) + 2H₂O(l) → 2KOH(aq) + 2H₂(g)

27.  When iron metal is placed into a solution of hydrochloric acid, will a reaction occur?  If so, what is the balanced equation for the reaction?

A)No reaction will occur.

B)Yes.  2Fe(s) + 2HCl(aq) → 2FeCl(aq) + H₂(g)

C)Yes.  Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)

D)Yes.  Fe(s) + 3HCl(aq) → FeCl₃(aq) + H₂(g)

28.  When copper metal is placed in a solution of zinc nitrate, will a reaction occur?  If so, what is the balanced equation for the reaction?

A)Yes.  Cu(s) + Zn(NO₃)₂(aq) → CuNO₃(aq) + ZnNO₃(aq)

B)Yes.  Cu(s) + Zn₂NO₃(aq) → CuNO₃(aq) + Zn(aq)

C)Yes.  Cu(s) + Zn(NO₃)₂(aq) → Cu(NO₃)₂(aq) + Zn(s)

D)No reaction will occur.

E)Yes.  Cu(s) + Zn₂NO₃(aq) → CuNO₃(aq) + 2Zn(aq)

29.  When heated, calcium carbonate (limestone) undergoes a decomposition reaction.  Write a balanced equation for this reaction.

A)CaCO₃(s) →  Ca(s) + CO₃(g)    D)2CaCO₃(s) →  2CaO(s) + CO₂(g)

B)CaCO₃(s) →  Ca(s) + CO₂(g)    E)2CaCO₃(s) →  2CaO(s) + 3CO₂(g)

C)CaCO₃(s) →  CaO(s) + CO₂(g)

30.  Which of the following ionic compounds would be expected to be insoluble in water?

A)  KCl    B)  PbI₂    C)  NH₄NO₃    D)  CuSO₄    E)  NaCH₃CO₂

31.  Which of the following ionic compounds would be expected to be insoluble in water?

A)  CaS    B)  Ca(NO₃)₂    C)  Na₂SO₄    D)  KI    E)  NaOH

32.  A 5.05 g sample of quartz (SiO₂) contains 2.36 g of silicon.  What are the percents of silicon and oxygen in quartz?

A)53.3% Si and 46.7% O

B)46.7% Si and 53.3% O

C)29.9% Si and 70.1% O

D)70.1% Si and 29.9% O

E)46.7% Si, and insufficient information to calculate % O

33.  A 6.25 g sample of magnetite (Fe₃O₄) contains 4.52 g of Fe.  What are the percents of iron and oxygen in magnetite?

A)28.6% Fe and 71.4% O D)27.7% Fe and 72.3% O

B)42.8% Fe and 57.2% O E)57.2% Fe and 42.8% O

C)72.3% Fe and 27.7% O

34.  A 7.50 g sample of pyrite (FeS₂) contains 3.49 g of iron.  What are the percents of iron and sulfur in pyrite (also known as "Fool's Gold" because of its golden color)?

A)57.4% Fe and 42.6% S  D)46.5% Fe and 53.5% S

B)66.7% Fe and 33.3% S  E)53.5% Fe and 46.5% S

C)33.3% Fe and 66.7% S

35.  Malachite is a green colored mineral that is 57.5% copper.  What mass of copper is present in a 250.0 g sample of malachite?

A)  63.6 g    B)  127 g    C)  435 g    D)  36.5 g    E)  144 g

36.  Barium sulfate is a compound used to assist in diagnosing medical problems through x-ray analysis and is 58.8% barium.  What mass of barium is present in a 620 mg tablet of barium sulfate?

A)  81 mg    B)  230 mg    C)  360 mg    D)  1100 mg    E)  11 mg

37.  Which of the following statements is incorrect?

A)PH₃ has 3 times as many hydrogen atoms as phosphorus atoms.

B)MgO has an equal number of magnesium ions and oxygen ions.

C)BaBr₂ has half as many barium ions as bromide ions.

D)N₂O₅ has 2.5 times as many nitrogen atoms as oxygen atoms.

E)SF₄ has 4 times as many fluorine atoms as sulfur atoms.

38.  Which of the following statements is incorrect?

A)CH₄ has ¼ as many carbon atoms as hydrogen atoms.

B)H₂O has twice as many oxygen atoms as hydrogen atoms.

C)SO₃ has three times as many oxygen atoms as sulfur atoms.

D)P₄O₁₀ has 2.5 times as many oxygen atoms as phosphorus atoms.

E)SrF₂ has twice as many fluoride ions as strontium ions.

39.  Which of the following statements is incorrect?

A)N₂H₄ has four times as many hydrogen atoms as nitrogen atoms.

B)SF₄ has ¼ as many sulfur atoms as fluorine atoms.

C)SO₂ has twice as many oxygen atoms as sulfur atoms.

D)Ca(NO₃)₂ has six times as many oxygen atoms as calcium ions.

E)H₂SO₄ has twice as many oxygen atoms as hydrogen atoms.

40.  How many moles are in a sample of ethylene glycol (commonly found in antifreeze), HOCH₂CH₂OH, that has a volume of 250.0 mL?  The molar mass and density of ethylene glycol are 62.07 g/mol and 1.11 g/mL, respectively.

A)4.47 molD)1.40 x 10⁴ mol

B)0.276 mol    E)1.72 x 10⁴ mol

C)3.63 mol

41.  How many oxygen atoms are in 75.0 g of SO₃?

A)225 atoms    D)1.69 x 10²⁴ atoms

B)0.937 atoms E)4.52 x 10²⁵ atoms

C)5.64 x 10²³ atoms

42.  What is the mass of 4.5 x 10²³ molecules of SO₂?

A)  2.9 x 10²⁵ g    B)  64 g    C)  86 g    D)  36 g    E)  48 g

43.  What is the mass of 2.4 x 10²³ molecules of NO₂?

A)  75 g    B)  18 g    C)  1.2 x 10² g    D)  1.1 x 10²³ g    E)  12 g

44.  Which of the following statements regarding empirical formulas, molecular formulas, and percent composition is correct?

A)The compounds NO₂ and N₂O₄ have the same empirical formula.

B)The compounds NO₂ and N₂O₄ have the same molecular formula.

C)The empirical formula of H₂O₂ is H₂O.

D)The empirical formula of N₂O₅ is NO_2.5.

E)The compounds PCl₃ and PCl₅ would have the same percent composition.

45.  Methyl butyrate is a compound that is partially responsible for the flavor of apples.  It consists of 58.80% C, 9.87% H, and 31.33% O.  What is the empirical formula of methyl butyrate?

A)  C₆H₁₀O₃    B)  C₅H₁₀O₂    C)  CH₂O    D)  C_4.9H_9.8O_1.9    E)  C₄H₉O₂

46.  Acetaminophen is the active ingredient in Tylenol.  It consists of 63.56% C, 6.00% H, 9.27% N, and 21.17% O.  What is the empirical formula of acetaminophen?

A)  C₈H₈NO₂    B)  C₈H₉NO₂    C)  C₆HNO₂    D)  C_5.3H_5.9N_0.7O_1.3    E)  C₄H₄NO

47.  Acetic acid has a molar mass of 60.05 g/mol and consists of 40.00% C, 6.714% H, and 53.29% O.  What is the molecular formula of acetic acid?

A)  C_3.33H_6.66O_3.33    B)  C₃H₆O₃    C)  CH₂O    D)  C₂H₄O₂    E)  CH₃O

48.  Butyric acid has a very unpleasant odor.  It is present in some rotting foods, body odor and vomit.  Butyric acid has a molar mass of 88.10 g/mol and consists of 54.53% C, 9.153% H, and 36.32% O.  What is the molecular formula of butyric acid?

A)  CH₂O_0.5    B)  CH₂O    C)  CH₄O    D)  C₂H₄O    E)  C₄H₈O₂

49.  Acetaminophen is the active ingredient in Tylenol.  It consists of 63.56% C, 6.00% H, 9.27% N, and 21.17% O.  What is the empirical formula of acetaminophen?

A)  C₈H₈NO₂    B)  C₈H₉NO₂    C)  C₆HNO₂    D)  C_5.3H_5.9N_0.7O_1.3    E)  C₄H₄NO

50.  Which of the following statements regarding empirical and molecular formulas is correct?

A)Information on percent composition is all that is necessary to determine both an empirical and a molecular formula.

B)A compound with an empirical formula of CH₂O and a molar mass of 90 g/mol would have a molecular formula of C₃H₆O₃.

C)The compounds C₂H₄ and C₃H₆ have different empirical formulas.

D)The formula Ca₂Cl₄ is the correct empirical formula for calcium chloride.

E)The compound benzene has a molecular formula of C₆H₆, so its empirical formula would be C₃H₃.