Question

A sample of a compound contains 65.4 grams of zinc, 12.0 grams of carbon, and 48.0 grams of oxygen. What is the mole ratio of zinc to carbon
to oxygen in this compound?
(1) 1:1:2 (3) 1:4:6
(2) 1:1:3 (4) 5:1:4

Answer 1

Moles= mass/mr

so moles of zinc= 65.4/65.4 = 1
moles of carbon= 12/12 = 1
moles of oxygen= 48/16 = 3 

so the ratio is 1:1:3 (2)

Answer 2

Answer: 2) 1:1:3

Explanation: First of all the given grams of each element are converted to moles and for this we divide the grams of an element by its atomic mass.

Atomic masses of Zn, C and O are as follows:

Zn = 65.4

C = 12.0

O = 16.0

moles of Zn = $\frac{65.4}{65.4}$  = 1

moles of C = $\frac{12.0}{12.0}$  = 1

moles of O = $\frac{48.0}{16.0}$ = 3

To get the mole ratio we divide the moles of each by the least one of them. The number which is least one of them is 1 and if we divide all of them by 1 then we get 1, 1 and 3 respectively.

So, the mole ratio of Zn:C:O in this compound is 1:1:3 and hence the second choice is correct.