Homework #2, Graded Answers
Chem20, Elementary Chemistry
Chapter Two
58.) Perform each calculation to the correct number of significant figures.
a.)
b.)
c.)
d.)
89.3 (3 sig. figs.) x 77.0 (3 sig. figs.) x 0.08 (1 sig. fig) = 550  600 (1 sig. fig.)
(5.01  105) (3 sig. figs.) ÷ (7.8  102) (2 sig. figs.) = 642  640 (2 sig. figs)
4.005 (4 sig. figs.) x 74 (2 sig. figs.) x 0.007 (1 sig. fig.) = 2.0  2 (1 sig. fig.)
453 (3 sig. figs.) ÷ 2.031 (4 sig. figs.) = 223.0  223 (3 sig. figs.)
66.) Perform each calculation to the correct number of significant figures.
a.) (1.7  106 ÷ 2.63  105) + 7.33 =
(6.46 (2 sig. figs) ) + 7.33 = 13.79 (1 decimal place)  13.8
b.) (568.99 – 232.1) ÷ 5.3
(336.89 (1 decimal place) ) ÷ 5.3 = 63.5 (2 sig. figs.)  64
c.) (9443 + 45 – 9.9) x 8.1  106
10
(9478.1 (ones position) ) x 8.1  106 = 7.67  1010 (2 sig. figs.)  7.7  10
d.) (3.14 x 2.4367) – 2.34
(7.651 (3 sig. figs.) ) – 2.34 = 5.311 (2 decimal places)  5.31
72.) Perform each conversion within the metric system.
a.) 1.08 Mm to kilometers
0 m
m
0
m
m
0 m
b.) 4.88 fs to picoseconds
0-
s
s
4.88  10-3 ps
s
s
0
- 2
1.08  103 km
s
c.) 7.39  1011 m to gigameters
m
2
0 m 0 m 7.39  10 Gm
d.) 1.15  10-10 m to picometers
1.15  102 pm
m
0- 0 m
0
- 2
m
83.) A runner wants to run 10.0 km. She knows that her running pace is 7.5 mi/hr. How many
minutes must she run?
00 m
mi
hr
m
mi
0 min
hr
49.6  50. or 5.0  10 minutes (2 sig. figs. from 7.5)
1
116.) A hybrid SUV consumes fuel at a rate of 12.8 km/L. How many miles can the car travel on
22.5 gallons of gasoline?
22
al
2
al
m
mi
m
677.0  677 miles