Chapter 2 Homework

1 What changes when an ion is formed from an atom?
A. Neutrons are lost or gained.
B. Protons are lost or gained.
C. The nucleus disintegrates.
D. Electrons are lost or gained.
E. Either protons or electrons are lost or gained.

2 When comparing a 10.00 g sample of iron with a 10.00 g sample of lead:
A. each sample has the same number of atoms.
B. there are more iron atoms than lead atoms.
C. there are more lead atoms than iron atoms.
D. it is not possible to tell which sample contains more atoms.
E. the lead is heavier than the iron, and therefore there would be more atoms.

3 The correct symbol for the ion formed by nitrogen is:
A. N2-
B. N3-
C. N3+
D. N2+
E. N-

4 Which of the following combinations of formula and name is incorrect?
A. hydroxide ion = OH
̅
B. nitrate ion = NO3
̅
C. sulfide ion = SO32
̅
D. nitrite ion = NO2
̅
E. sulfate ion = SO42
̅
5 How many molecules are in 0.25 mole of Na2O?
A. 4.5 × 10(23)
B. 0.75
C. 1.5 × 10(23)
D. 4.2 × 10(
̅
25)
E. 0.25

6 Calculate the molar mass of Na2SO4.
A. 94.05 g/mol
B. 71.06 g/mol
C. 142.05 amu
D. 142.05 g/mol
E. 94.05 amu

7 If 4.05 × 1023 molecules of a substance have a mass of 86.2 g, what is the molar mass of the substance?
A. 128 g/mol
B. 3.49 × 1025 g/mol
C. 2.13 × 1022 g/mol
D. 4.70 × 1021 g/mol
E. 58.0 g/mol

8 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
B. 42.8% Fe and 57.2% O
C. 72.3% Fe and 27.7% O
D. 27.7% Fe and 72.3% O
E. 57.2% Fe and 42.8% O

9 Acetic acid is the active ingredient in vinegar. It consists of 40.00% C, 6.73% H, and 53.28% O. What is the empirical formula of acetic acid?
A. C3.33H6.66O3.33
B. C3H6O3
C. CH2O
D. C2H4O2
E. CH3O

10 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