Chemistry 111 Study Sheet Answers
Test 3 (Chapters 3)
1. amu is an abbreviation for atomic
mass units .
2. What is the formula mass of NaOH? 40.00
3. Find the molecular mass of the following.
What is the mass of 2.7moles NaOH?
a. C5H12
110 g (2 sig. fig.)
72.15; b. Al(NO3)3 213.0
4.
6.022x1023 molecules of NaH = 1 mole of NaH molecules.
5.
9.012 grams Be atoms = 1 mole of Be atoms
6. How many moles of Na2SO4 are in a 1.5 g sample of Na2SO4? 0.01056 rounds to 0.011
How many moles of O atoms are in the same sample?
7. Calculate the % composition of C and H in CH4.
8. Determine the percent composition of C8H10O2.
9. What is the empirical formula for C9H12O3?
0.01056x4 = 0.042
mol Na2SO4
mol of O atoms
C 74.87%; H 25.13%
C 69.54%; H 7.296%; O 23.16%
C3H4O
10. Determine the empirical formula for a compound with a percent composition of 45.0%C; 7.50%H; and 47.5%F.
percent—>mass—>moles—>mole ratio—>empirical formula
C3H6F2
C5H8O2
11. Calculate the empirical formula of a polymer which is made of 59.9% C, 8.06% H, and 32.0 % O.
12. A 27.5 g sample of a compound containing carbon and hydrogen contains 5.5 g of hydrogen. The molecular mass of the
compound is approximately 30 amu. What are the empirical and molecular formulas?
CH3
C2H6
13. Balance the following chemical equations.
a.
2 KClO3 →
2 KCl +
3 O2
b. Ca3(PO4)2
+
8C →
Ca3P2
+
8 CO
2 Na2S2O3 + I2 → 2 NaI + Na2S4O6
14. Balance the following equations:
2 C3H6 + 9 O2 → 6 CO2 + 6 H2O
2 HCl + Cr → CrCl2 + H2
15. List a) the product(s), and b) the reactant(s) in the equation:
(Reactant: KClO3 ) → (Products:
KCl +
O2)
16. Given the balanced equation {2Al + 3H2SO4 → Al2(SO4)3 + 3H2} answer the following:
a) How many moles of Al2(SO4)3 can be produced by reacting 0.50mol H2SO4?
0.17 mol Al2(SO4)3
b) How many moles of Al2(SO4)3 can be produced by reacting 18g H2SO4?
0.061 mol Al2(SO4)3
c) How many grams of H2 can be produced by reacting 18g Al?
2.0 g H2
d) If 1.00mol Al is reacted with 1.25 mol H2SO4, which is the limiting reagent?
e) How many grams of H2 could be produced by the reaction in question d?
f) What is the limiting reagent if 54g Al is reacted with 98g H2SO4?
H2SO4
2.5 g H2
H2SO4
g) What is the percent yield if 87g of Al2(SO4)3 is produced by the reaction in question f?
76%
17. 1.50 g of silicon and 1.50 g of nitrogen can be combined according to the following reaction:
Si + N2 → Si3N4
a. What is the limiting reagent? Si b) What is the theoretical yield of Si3N4?
18. What is the % yield of a reaction that converts 1000.0 g of C6H5CH3 to 1210.0 g of C6H5CO2H?
2 C6H5CH3 + 3 O2 → 2 C6H5CO2H + 2 H2O
91.29%
2.50 g Si3N4