Question

Nitrogen has a density of 1.17×10−3g/cm3.

What is the correct mass for 2,500 cm3 of nitrogen gas using significant figures?

Responses

2.92 g

2.92 g

2.9 g

2.9 g

2.2×106 g
2.2 times 10 to the power of 6 lowercase g

14×106 g

Answer 1

Mass = density × volume = (1.17×10^−3 g/cm^3)(2500 cm^3) = 2.925 g.

Significant-figure rule: use the least number of sig figs in the inputs. "2,500" (with no decimal or bar) is typically taken as having 2 sig figs, so round 2.925 to 2 sig figs → 2.9 g.

(If 2,500 were written to show 3 sig figs, the answer would be 2.92 g.)