Question

Which equivalence factor should you use to convert from 106 grams of O2 to moles of O2?

A.(1 mol O2/16.00 grams O2)

B.(16.00 grams O2/1 mol O2)

C.(1 mol O2/32.00 grams O2)

D.(32.00 grams O2/1 mol O2)

Pls help for exam

Answer 1

C. (1 mol O2/32.00 g O2)

To convert 106 g O2 to moles of O2, the equivalence factor is either

(1 mol O2/32.00 g O2) or (32.00 g O2/1 mol O2). We choose the one that has the desired units (mol) on top: (1 mol O2/32.00 g O2). Then,

Mass of O2= 106 g O2× (1 mol O2/32.00 g O2) = 3.31 mol O2

Notice that the unwanted units (g O2) cancel and do not appear in the answer.

“A. (1 mol O2/16.00 g O2)” is incorrect because it uses the molar mass of O (not O2).

”B. (16.00 grams O2/1 mol O2) is incorrect because it uses the wrong molar mass for O2.

“D. (32.00 g O2/1 mol O2)” is incorrect because it has the equivalence factor upside down.