CHEM 160, Fall 2008 Name_____________________________
Exam #3 (Chp 9 and 10) 100 points total Page 1 of 4
Answer Questions 1-15 on your scantron. Each question is worth 2 pt.
1. (9.1) A compound contains sodium and fluorine in the ratio 1.21 sodium : 1 fluorine. How much fluorine is there in
a sample of this compound that contains 34.5 g of sodium?
A) 15.6 g B) 28.5 g C) 41.8 g D) 76.2 g
2. (9.2) What is the formula mass of Al(ClO)3
A) 78.43 B) 110.43 C) 132.39 D) 181.33 E) 235.29
3. (9.4) A 2.45 g sample of strontium completely reacts with 0.44 g oxygen to make 2.89 g strontium oxide. What is
the percent oxygen in strontium oxide?
A) 15.2 % B) 18.0% C) 45.9% D) 54.12% E) 84.8%
4. (9.5) How many moles lead are there in 4.6 x 1024 lead atoms (207.2 g/mol)?
A) 0.13 B) 7.6 C) 210 D) 2.1 x 104E) 1.25 x 1029
5. (9.5) How many molecules are there in 1.55 mol of water (18.02 g/mol)?
A) 11.6 B) 27.9 C) 2.57 x 10-24 D) 9.33 x 1023
6. (9.6) How many grams are there in 1.55 mol of water (18.02 g/mol)?
A) 11.6 B) 27.9 C) 2.57 x 10-24 D) 9.33 x 1023
7. (9.6) How many moles are there in 100.0 g of Fe2O3 (159.70 g/mol)?
A) 15970 mol B) 6.022 x 1025 C) 0.6262 mol D) 0.626 mol E) 1.597 mol
8. (9.8) A 0.123 mol sample of a pure substance has a mass of 5.904 g. What is the molar mass of the substance?
A) 0.0208 g B) 0.726 g C) 5.904 g D) 48.0 g
9. (9.9) Which of the following pairs of mole amounts of compounds contain the same mol of nitrogen atoms?
A) 0.5 mol NH3 / 0.5 mol N2O5B) 1.0 mol NH3 / 0.5 mol N2O5C) 0.5 mol NH3 / 1.0 mol N2O5
10. (9.12) In which of the following (mark all that apply) are empirical / molecular formulas correctly matched?
A) CH4 / C2H8B) NO2 / N2O2C) BF3 / BF3D) CH2O / C6H12O6E) MnCl2 / MnCl5
11. (10.1) Indicate the missing words in the following statement: "For an ordinary chemical reaction the mass of the
products is ________ the mass of the reactants."
A) usually more than B) always less than C) usually less than D) always equal to
12. (10.2) Which of the following elements is represented by a diatomic molecule in a chemical equation?
A) beryllium B) boron C) chlorine D) krypton E) phosphorous
13. (10.3) In a valid chemical equation ________.
A) only reactants and products that are solids or liquids are listed
B) the number of products must equal the number of reactants
C) the total number of molecules on each side of the equation must be equal
D) the reactants always appear on the left-hand side of the equation
14. (10.6) Which one of the following conversion factors is not consistent with the equation
4NH3 + 5 O2 4NO + 6H2O
A) (5 moles O2/6 moles H2O)
B) (4 moles NO/5 moles O2)
C) (4 moles NH3/5 moles H2O)
D) (4 moles NO/4 moles NH3)
