Question

The molar mass of ${O_2}$​ is $32\,\,gram\,\,per\,\,mole$. How many moles are there in $10\,\,grams$ of oxygen?
A. $3.2$
B. $320$
C. $0.3125$
D. $0.42$

Answer 1

To solve this question, we must first have some knowledge of Basics of mole concept and Unitary method of solving equations. Then we need to use the molecular formula and the molar mass and to obtain the number of moles, then divide the mass of the compound by the molar mass of the compound expressed in grams and then only we can conclude the correct answer.

Complete answer:
Before we move forward with the solution of this given question, let us first understand some basic concepts:
A mole is defined as the mass of the substance which consists of the equal quantity of basic units, these basic units can be atoms, molecules or formula units based on the substance.
One mole of any substance is equal to the value of $6.022 \times {10^{23}}$ (Avogadro number). It can be used to measure the products obtained from the chemical reaction. The unit is denoted by mol. It can be given by:
$Number\,\,of\,\,moles\,\, = \,\,\dfrac{{Given\,\,Mass}}{{Molar\,\,Mass}}$
Step 1: In this step we will find the No. of moles of Oxygen in $10\,\,grams$ of Oxygen
In the given question the molar mass is $32\,\,gram\,\,per\,\,mole$ and the given mass is $10\,\,grams$. So, by applying the formula:
Number of moles of Oxygen $= \dfrac{{10}}{{32}} = 0.3125$
So the required number of moles of oxygen is $0.3125$
**So, clearly we can conclude that the correct answer is,‘ C. $0.3125$’. **

Note: We must always keep in mind to change all the units in the SI unit while solving the problems as a general practice. Keep in mind that molar mass and molecular mass is two different concepts, don’t get confused.