chemxsup11_12

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					                                      Ch. 11-12 Problem Sets
                        (Please answer all problems on a separate sheet of paper.)

Problem Set 11.1 – mole wheel problems
HOMEWORK OPTIONS: 1) Do all problems a-f and have your total score out of 48 points. 2) Do all
    problems, but omit parts d,e,f for a total of 32 points. (I will have two different columns in my grade
    book. One with the larger point total, and one with the smaller point total.) Do what you feel is an
    appropriate amount of practice so that you are confident with these calculations.)
1) a. What is the definition of a mole?
    b. How many particles in a mole?
    c. What is the name given to the number of particles in a mole?
2) What is the molar mass of each of the following elements/compounds?
    (Mrs. Grack’s/Mrs. Hagen’s students round to the tenths place.)
    a. Lithium, Li                                 d. aluminum hydroxide, Al(OH)3
    b. Carbon, C                                   e. dinitrogen pentoxide, N2O5
    c. carbon dioxide, CO2                         f. aluminum sulfate, Al2(SO4)3
3) Convert the following masses to number of moles.
    a. 2.00 g Lithium metal, Li                    d. 92.7 g solid potassium, K
    b. 58.5 g oxygen gas, O2                       e. 120. g sulfur dioxide gas, SO2
    c. 80. g ammonia (NH3) gas                     f. 5.00 g copper metal, Cu
4) Convert the following volumes at STP to moles. .
    a. 2.00 L argon gas, Ar                        d. 95.0 L nitrogen gas, N2
    b. 18.5 L methane gas, CH4                     e. 130. L sulfur dioxide gas, SO2
    c. 80. L ammonia (NH3) gas                     f. 5.00 L helium gas, He
5) Convert the following numbers of representative particles to moles.
    a. 2.12 x 1024 atoms argon gas, Ar                         d. 4.5 x 1023 atoms nickel metal, Ni
                 23
    b. 3.01 x 10 molecules of methane gas, CH4                 e. 1.80 x 1024 molecules water, H2O
                  23
    c. 7.25 x 10 molecules of ammonia (NH3) gas                f. 5.00 x 1022 molecules sugar, C12H22O11
6) Convert the following.
    a. How many grams of oxygen gas, O2, in a 25.0 L sample at STP?
    b. How much space would 2.50 x 1024 molecules of carbon dioxide, CO2, occupy at STP?
    c. How many molecules of ammonia gas (NH3) would have a mass of 45.0 grams?
    d. How many atoms in a 20.0 gram sample of carbon, C?
    e. How much space would 80.0 grams of nitrous oxide (N2O) occupy at STP?
    f. How many molecules in 40.0 g of water, H2O?
7) Balance the following chemical equations.
    a. Ba(NO3)2 (aq) + K2SO4 (aq)  BaSO4 (s) + KNO3 (aq)
    b. C3H8 (g) +O2 (g)  CO2 (g) + H2O(l)
    c. Li3PO4 (aq) + AgNO3 (aq)  Ag3PO4 (aq) + LiNO3 (aq)
    d. CaS (aq) + HCl(aq)  H2S (g) + CaCl2 (aq)
    e. Al(OH)3 (aq) + H2SO4 (aq)  H2O (l) + Al2(SO4)3 (aq)
    f. C4H10 (g) +O2 (g)  CO2 (g) + H2O(l)
8) If I had a mole of dollars to distribute among all the people on the world, how many dollars would
    each person get. (World population ~6 billion)
9) How many atoms in 20.0 grams of water?
EC) How many molecules of C3H8O can be made from 2 moles of hydrogen atoms (assuming you have
    enough carbon and oxygen)?




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Problem Set 11.2 – empirical/molecular formula
1) The following are formulas for many compounds that exist in nature. Write the empirical formula for
    each. a. H2O2 b. N2O4 c. C12H22O11 d. P2O5 e. C2H5OH f. C8H18
2) C2H3O is the empirical formula for a compound. List three possible molecular formulas.
3) A 20-gram sample of unknown is found to contain 12.4 g carbon, 2.06 g hydrogen, and 5.52 g oxygen.
    a. What is the empirical formula for this compound?
    b. If the molar mass of the compound is 174 grams, what is the molecular formula?
4) An unknown is found to be 47.4% carbon, 10.5% hydrogen, and 42.1% oxygen.
    a. What is the empirical formula for this compound?
    b. If the molar mass of the compound is 76 grams, what is the molecular formula?
5) 30.0 grams of hydrated magnesium sulfate, MgSO4•X H2O, is heated strongly. After heating, the
    remaining mass is 14.7 grams. What must be the formula of the hydrated solid? (i.e. You must
    determine the value of “X” in the formula provided.)
6) An unknown is found to contain 0.187 mol carbon atoms, 0.561 mol hydrogen atoms, and 0.0935 mol
    oxygen.
    a. What is the empirical formula for this compound?
    b. If the molar mass of the compound is 46.0 grams, what is the molecular formula?
7) An unknown is found to be 48.6% carbon, 8.1% hydrogen, and 43.2% oxygen.
    a. What is the empirical formula for this compound?
    b. If the molar mass of the compound is 147.6 grams, what is the molecular formula?
8) 55.0 grams of hydrated copper (II) sulfate, CuSO4•X H2O, is heated strongly. Heating causes the mass
    to decrease by 19.8 grams. What must be the formula of the hydrated solid?

Problem Set 12.1 – 3-step mole method & related problems; hydrates
(Homework Option do 1-11 and 17 OR               1-18.)
1) NaOH + HCl  H2O + NaCl
    If 3 moles of sodium hydroxide react…
    a. How many moles of HCl will be needed?
    b. How many moles of water will be formed?
    c. How many moles of sodium chloride will be formed?
2) 2 AgNO3 (aq) + BaCl2 (aq)  2 AgCl (s) + Ba(NO3)2 (aq)
    If 5 moles of barium chloride react…
    a. How many moles of silver nitrate will be needed?
    b. How many moles of precipitate, AgCl, will be formed?
3) N2 (g) + 3 H2 (g)  2 NH3 (g)
    If 6 moles of hydrogen react…
    a. How many moles of nitrogen will be needed?
    b. How many moles of ammonia will be formed?
4) NaOH + HCl  H2O + NaCl.
    If 35.0 moles of sodium hydroxide react…
    a. How many grams of HCl will be needed?
    b. How many moles of water will be formed?
    c. How many grams of sodium chloride will be formed?
5) 2 AgNO3 (aq) + CaCl2 (aq)  2 AgCl (s) + Ca(NO3)2 (aq) .
    If 87.2 grams of silver nitrate react…
    a. How many molecules of calcium chloride will be needed?
    b. How many grams of precipitate, AgCl, will be formed?
6) Write the balanced equation for nitrogen gas, N2, reacting with hydrogen gas, H2, to make ammonia,
    NH3 (g).
    If 2.25 moles of hydrogen react…
    a. How many liters of nitrogen will be needed (@STP)?
    b. How many grams of ammonia will be formed?
7) a. Write the balanced equation for when sodium sulfide, Na2S, and silver nitrate, AgNO3, react to
    form aqueous sodium nitrate, NaNO3, and the precipitate, silver sulfide, Ag2S.
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    If 2.25 grams of sodium sulfide react…
    b. How many grams of silver nitrate are needed?
    c. How many grams of silver sulfide, Ag2S, will be formed?
8) The molecular weight of AX6 = 146.1 g/mol. X is diatomic. What is the molecular weight of X if the
    atomic weight of A is 32.1 g/mol?
9) Two moles of a sulfur oxide, S?O?, decompose to produce 2 moles of sulfur and 3 moles of oxygen.
    What is the molecular formula for this sulfur oxide? (i.e. determine the values for the subscripts in
    S?O?.)
10) What represents the least number of water molecules?
    a. 36.0 g             b. 1 molar mass         c. 7 moles      d. 3.5 x 1020 molecules
11) Use the following equation to answer the questions below.
                 2 H2 + O2  2 H2O + 126 kcals
         a. How many moles of oxygen are needed to produce 55.0 grams of water?
         b. How many kilocalories of energy are produced from the reaction of 44.8 liters of hydrogen?
         c. If 750. kcal of energy are released, how many grams of each reactant were needed?
12) Complete the following:
    a. How many grams of ammonia (NH3) in 55.0 L at STP?
    b. What’s the mass of 3.5 x 1024 molecules of oxygen, O2?
    c. How much space would 5.25 moles of nitrous oxide gas occupy at STP?
13) Write the balanced equation for copper (II) nitrate, Cu(NO3)2, reacting with zinc metal, Zn, to
    produce copper metal, Cu, and zinc nitrate, Zn(NO3)2.
    If 42.0 g of zinc react…
    a. How many moles of copper (II) nitrate will be needed?
    b. How many grams of copper metal will be formed?
14) Write the balanced equation for the combustion of methane gas (CH4). Combustion is when a
    hydrocarbon (like CH4) reacts with oxygen gas, O2, to produce water and carbon dioxide.
    If 5.0L of methane react at STP …
    a. How many liters of carbon dioxide will be formed?
    b. How many grams of oxygen will be needed?
15) Write the balanced equation for the synthesis of hydrogen bromide gas, HBr, from hydrogen gas, H2,
    and liquid bromine, Br2. (If hydrogen bromide is synthesized, that means it is made. i.e. HBr is the
    product.)
    If 1.4 moles of hydrogen bromide are formed, how many grams of each reactant were needed?
16) a. Write the balanced equation for the combustion of ethane, C2H6. (Remember: Combustion is
    when a hydrocarbon reacts with oxygen gas, O2, to produce water and carbon dioxide.)b. If 4.5 moles
    of ethane react how many grams of water will be formed? c. How many liters of carbon dioxide will
    be formed (@ STP)?
17) 30.0 grams of hydrated magnesium sulfate, MgSO4•X H2O, is heated strongly. After heating, the
    remaining mass is 14.7 grams. What must be the formula of the hydrated solid? (i.e. You must
    determine the value of “X” in the formula provided.)
18) 55.0 grams of hydrated copper (II) sulfate, CuSO4•X H2O, is heated strongly. Heating causes the
    mass to decrease by 19.8 grams. What must be the formula of the hydrated solid?




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Problem Set 12.2 – 3-step mole method & related problems continued
1) K2CrO4 (aq) + BaCl2 (aq)  2 KCl (aq) + BaCrO4 (s)
    If 5 moles of barium chloride react…
    a. How many moles of precipitate (solid BaCrO4) will be produced?
    b. How many moles of potassium chloride, KCl, will be produced?
2) 4 Fe (s) + 3 O2 (g)  2 Fe2O3 (s)
    If 6 moles of oxygen react…
    a. How many moles of iron will be needed?
    b. How many moles of iron (II) oxide, Fe2O3, will be formed?
3) 2 AgNO3 (aq) + CaCl2 (aq)  2 AgCl (s) + Ca(NO3)2 (aq) .
    If 87.2 grams of silver nitrate react…
    a. How many molecules of calcium chloride will be needed?
    b. How many grams of precipitate, AgCl, will be formed?
4) Write the balanced equation for chlorine gas, Cl2, reacting with hydrogen gas, H2, to make hydrogen
    chloride gas, HCl.
    If 2.25 moles of hydrogen react…
    a. How many liters of chlorine will be needed (@STP)?
    b. How many grams of hydrogen chloride, HCl, will be formed?
5) a. Write the balanced equation for when potassium carbonate, K2CO3, and copper (II) chloride, CuCl2,
    react to form potassium chloride, KCl, and copper (II) carbonate, CuCO3.
    If 15.35 grams of copper (II) chloride, CuCl2, react…
    b. How many grams of potassium carbonate are needed?
    c. How many grams of potassium chloride, KCl, will be formed?
6) Element A is diatomic. Element B is monatomic. One mole of element A combines with two moles
    of element B to form 2 moles of compound C. The atomic weight of A is 1.0 g; the atomic weight of
    B is 35.0g.
    a. What is the molecular weight               of A? ______
                                                  of B? ______
                                                  of C? ______
    b. What is the formula (using the elements A and B) of C?
7) A. If 8.20 liters of a diatomic gas at STP weigh 25.4 grams, what is the molar mass of the gas?
    (HINT: Think unit analysis. What units would your answer be for molar mass?)
    B. What is the probable identity of that gas – hydrogen (H2), nitrogen(N2), oxygen(O2), fluorine(F2),
         or chlorine Cl2),?
8) Use the following equation to answer the questions below.
                  C3H8 + 5 O2  3 CO2 + 4 H2O + 393.5 kJ
         a. How many liters of oxygen are needed to produce 0.200 mol of water?
         b. How many kilojoules of energy are produced from the reaction of 5.0 L of oxygen?
         c. If 924 kJ of energy are released, how many grams of propane, C3H8, were needed?

Problem Set 12.3 – limiting reactant, %error, %yield (Option: 1-9 OR 1-12)
1) NaOH(aq) + HCl(aq)  H2O(l) + NaCl(aq)
    If 3.0 moles of sodium hydroxide and 4.0 moles of hydrochloric acid react…
    a. What’s your limiting reactant?
    b. How many moles of excess reactant remain?
    c. How many grams of each product will be formed?
2) 2 H2 (g) + O2 (g)  2 H2O (g
    If 5.0 moles of hydrogen and 3.0 moles of oxygen react…
    a. What’s your limiting reactant?
    b. How many moles of excess reactant remain?
    c. How many grams of excess reactant remain?
    d. How many grams of water will be formed?
    e. If you made 85.0 grams of water, what is your percent yield?
    f. If you made 85.0 grams of water, what is your percent error?
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3) a. Write the balanced equation for the reaction of aqueous sulfuric acid, H2SO4, and solid aluminum
       hydroxide, Al(OH)3 forming liquid water and aqueous aluminum sulfate, Al2(SO4)3.
    If 30.0 grams of sulfuric acid and 25.0 grams of aluminum hydroxide react…
    b. How many grams of each product will be formed?
    c. How many grams of excess reactant remain?
4) a. Write the balanced equation for lithium metal, Li, reacting with aqueous copper (II) nitrate,
        Cu(NO3)2, to produce copper metal, Cu, and aqueous lithium nitrate, LiNO3.
    b. If 15.0 grams of lithium react, what is your theoretical yield of copper?
    c. If you produce 62.4 grams of copper, what is your percent yield?
    d. If you produce 62.4 grams of copper, what is your percent error?
5) a. Write the balanced equation for aqueous iron (III) hydroxide, Fe(OH)3, reacting with aqueous nitric
        acid, HNO3, to produce aqueous iron (III) nitrate, Fe(NO3)3 and liquid water.
    b. If you react 10.7 g iron (III) hydroxide with 6.30 grams of nitric acid, how many milliliters of
    water should be formed? (density of water = 1g/mL)
6) a. Write the balanced equation for aqueous lead (II) nitrate, Pb(NO3)2, reacting with aqueous sodium
        chloride, NaCl, to produce aqueous lead (II) chloride, PbCl2 and aqueous sodium nitrate, NaNO3.
   b. If you react 6.62 grams of lead (II) nitrate, Pb(NO3)2, with 11.7 grams of sodium chloride, NaCl,
        how many grams of solid lead (II) chloride, PbCl2, will be produced?

7) Given the following equation, answer the questions below:
                                4 Fe(s) + 3 O2 (g)  2 Fe2O3 (s) + 1652 kJ
   a. If 20.0 g iron react with 6.72 L of oxygen gas, what is the limiting reactant?
   b. How many grams of iron (III) hydroxide, Fe2O3, will be formed?
   c. How much heat (in kJ) will be produced?

8) Given the following balanced equations, how many grams of gold can be produced from 2.00 grams of
    zinc oxide? (Hint: Because there are two reactions, you will need to use two mole ratios.)
                                  2 ZnO (s) + C (s)  2 Zn (s) + CO2 (g)
                               2 Au3+ (aq) + 3 Zn (s)  3 Zn2+ (aq) + 2 Au (s)
9) Is it possible to have more than 100% yield? Explain.

10) a. Write the balanced equation for solid calcium oxide, CaO, reacting liquid water to produce
    aqueous calcium hydroxide, Ca(OH)2.
    b. If you react 10.0 g calcium oxide in 250. mL of water, how many grams of calcium hydroxide
    should be formed? (density of water = 1g/mL)
11) a. Write the balanced equation for gaseous nitrogen, N2, reacting with gaseous oxygen, O2, to form
    gaseous nitrogen monoxide, NO.
    b. If you react 4.48 L nitrogen with 5.00 L oxygen, how many liters of nitrogen monoxide should be
    formed?
12) Given the following equation, answer the questions below:
                           CaC2 (s) + 2 H2O(l)  Ca(OH)2 (aq) + C2H2 (g) + 713 kJ
    a. If 3.50 g iron react with 2.00 g of water, what is the limiting reactant?
    b. How many grams acetylene, C2H2, will be formed?
    c. How much heat (in kJ) will be produced?




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