STOICHIOMETRY QUIZ Part I

1. Sodium is a soft, reactive metal that instantly reacts with water to give hydrogen gas and a solution of sodium hydroxide. Ar Na = 23; Ar H = 1; Ar O = 16. The mass of sodium which needed to give 2,24 L at STP is ….
a. 1,2 g
b. 2,3 g
c. 4,6 g
d. 5,7 g
e. 8,0 g
2. A solution of sodium carbonate is added to a solution of hydrochloric acid. If the mass of sodium carbonate is 2,12 grams (Mr = 106), the volume of the gas produced at STP is ….
a. 112 cm3
b. 224 cm3
c. 336 cm3
d. 448 cm3
e. 560 cm3
3. A 5,72 g of Sodium carbonate deka hydrate (Mr = 286) is heated to form sodium carbonate anhydrate (Mr = 106). The correct statement about this reaction is ….
a. the type of reaction is cristalization
b. Na2CO3.10H2O(s) à Na2CO3(s) + 10H2O(g)
c. the amount of reactant is 0,01 mol
d. the salt produced is 0,01 mol
e. the mass of the product is 1,06 g
4. Calcium reacts with water according to the following reaction. At STP, what volume (L) of hydrogen would be produced by the reaction of 1.2 grams of calcium? (Ar: Ca = 40, H = 1, O = 16).
Ca(s) + 2 H2O(l) --> Ca(OH)2(aq) + H2(g)
a. 335
b. 440
c. 540
d. 671
e. 585
5. A commercial drain cleaner results in the following reaction in a clogged drain. What volume of H2 (L) at STP is produced when 4.25 g of aluminum reacts? (Ar: Al = 27, Na = 23, O = 16, H = 1).
2 NaOH(aq) + 2 Al(s) + 6 H2O
2 NaAl(OH)4(aq) + 3 H2(g)
a. 6.01
b. 2.44
c. 4.56
d. 5.29
e. 3.33
6. Pure tungsten can be prepared by the following reaction. What volume (L) of H2 at 0.980 atm and 20oC is required to react with 25.2 g of WO3? (Ar: W = 184, H = 1, O = 16).
3 H2(g) + WO3(s) --> W(s) + 3 H2O(g)
a. 7.20
b. 2.67
c. 9.00
d. 8.00
e. 4.50
7. A 3.040 g sample of impure calcium phosphide reacts with water to give 685 mL of PH3 at 20oC and 745 mm Hg. What is the % Ca3P2? (Ar: Ca = 40, P = 31, H = 1, O = 16).
Ca3P2(s) + 6 H2O(l) --> 3Ca(OH)2(s) + 2 PH3(g)
a. 83.9
b. 85.9
c. 76.2
d. 88.2
e. 80.8
8. An alloy consists of 5.0% Cu and 95.0% Al. Aluminum reacts with HCl but copper does not. What mass of alloy is required to produce 1.96 g of hydrogen gas? (Ar Al = 27, H = 1, Cl = 35.5).
2 Al + 6 HCl --> 2 AlCl3 + 3 H2
a. 17.5
b.18.4
c. 23.0
d. 1
e. 27.6
9. The mass of H2 produced by reaction of 1.60 g Fe and 2.00 g HCl is 0.0505 g. What is the percent yield? (Ar Fe = 56, Cl = 35.5, H = 1).
Fe + 2 HCl --> FeCl2 + H2
a. 89
b. 90
c. 92
d. 91
e. 90
10. The mass of H2 produced by reaction of 1.80 g Al and 6.00 g H2SO4 is 0.112 g. What is the percent yield? (Ar Al = 27, S = 32, O = 16, H = 1).
2 Al + 3 H2SO4 --> Al2(SO4)3 + 3 H2
a. 92.4
b. 93.4
c. 93.0
d. 90.8
e. 94.5