Question

What is the weight of 0.1 moles of $N{{a}_{2}}C{{O}_ {3}}$
(A) 10g
(B) 5g
(C) 10.6g
(D) 12.6g

Answer 1

To find the atomic weight of the given compound we will be using the formula: number of moles = weight $\div$ molar mass as we have been given the number of moles of $N{{a}_{2}}C{{O}_ {3}}$.

Complete answer:
We have been provided that the number of moles of $N{{a}_{2}}C{{O}_ {3}}$ are 0.1 moles,
We need to find the atomic weight,
So, for that:
We will be using the formula: number of moles = weight $\div$ molar mass,
And we have been provided that number of moles of $N{{a}_{2}}C{{O}_ {3}}$ is 0.1 moles,
And we can find the molar mass of $N{{a}_{2}}C{{O}_ {3}}$,
Molar mass of any compound can be easily be calculated by simply adding the standard atomic masses of the constituent elements,
So, we will find the molar mass of $N{{a}_{2}}C{{O}_ {3}}$, by the adding the atomic weights of Na, C and O:
Which would be come out to be: $(23\times 2) +12+(3\times 16) =46+12+48$,
So, the molar mass of $N{{a}_{2}}C{{O}_ {3}}$ comes out to be: 106,
Now keeping these values in the formula: number of moles = weight $\div$ molar mass,
So, the equation would be: $0.1=\dfrac{weight}{106}$,
So, the weight comes out to be: $0.1\times 106=10.6g$,
So, the weight of $N{{a}_{2}}C{{O}_ {3}}$ comes out to be 10.6g.

So, we can conclude that the correct option is (C).

Note:
$N{{a}_{2}}C{{O}_ {3}}$ is also known as washing soda and it has a lot of application, as it is used as a cleansing agent for household purposes, even for removing the hardness of water, to manufacture glass, soap and paper.