Question

What is the percent by mass of $NaHC{{O}_{3}}$ in a solution containing $20g$ $NaHC{{O}_{3}}$ ,dissolved in $600ml$ ${{H}_{2}}O$ ?

Answer 1

Hint : To find the percentage composition by mass of any compound, the only we need to know is the molecular formula of the compound and about the concept of solute and solvent so that we can use the formula of (w/w) % to calculate percentage by mass.

Complete Step By Step Answer:
Let’s understand some terms and then proceeds toward our question
Solvent: it is the component of the solution which is present in the greatest amount, and it is the amount which dissolves the solute particles.
Solute: it is the component of the solution which is present in the least amount, and it is the amount which dissolves in the solvent particles.
A solution is made up of solute and solvent together and in this question solute particle is $NaHC{{O}_{3}}$ (which is $20g$ ) and solvent is ${{H}_{2}}O$ (which is $600g)$ .
The mass of solute= $20gNaHC{{O}_{3}}$ and mass of the solution = $(NaHC{{O}_{3}}+{{H}_{2}}O)$ = $(600+20=620g)$ solution.
To calculate the percentage by mass of any compound we find the ratio of “The mass of solute to the whole compound(solution).
Formula(w/w) % = mass of $NaHC{{O}_{3}} \times 100$ / mass of the solution $(NaHC{{O}_{3}}+{{H}_{2}}O)$ .
(w/w) % = $(20g+620g) \times 100=3\cdot 2$ ,
Therefore, the percentage by mass of $NaHC{{O}_{3}}$ $=3\cdot 2$ .

Note :
In such a type of question, we only have to check which is solute and which one is solvent so that we can directly use the formula of “(w/w) %= mass of solute/mass of solvent” and get the desired product.