Question

Which equivalence factor should you use to convert from 38.2 grams of K to moles of K?
a
(38.2 g K/39.10 g K)
b
(38.2 g K/1 mol K)
c
(1 mol K/38.2 g K)
d
(1 mol K/39.10 g K)

Answer 1

In order convert the mass of a substance to its number of moles The conversion factor is the reciprocal of the molecular weight of the substance. Hence, for the given element in the problem- potassium, the equivalence factor is d. (1 mol K/39.10 g K). 

Answer 2

Answer: (38.2 g K/39.10 g K)

Explanation:

To convert given masses into moles we use the formula :

Moles of K=$\frac{\text{ given mass of K}}{\text{ molar mass of K}}$

Given:

Mass of K= 38.2 grams

Molar mass of K=  39.10 g/mol

Putting in the values in the given formula, we get:

Moles of K= $\frac{38.2g}{39.10g/mole}=0.98moles$

Thus the moles are 0.98 moles.