Question

$117$ grams of $NaCl$ are dissolved in water to make $500mL$ of solution. Water is then added to this solution to make a total of one liter of solution. The final molarity of the solution is :

• A. $4M$
• B. $2M$
• C. $1M$
• D. $0.5M$
• E. $0.585M$

Answer 1

Answer: (B)

$2M$

The molar mass of $NaCl$ is $23+35.5=58.5$ g/mol.
The mass of $NaCl$ is $117$ grams.
The number of moles of $NaCl$ is $\frac{117}{58.5}=2$ moles.
Molarity of solution is the number of moles of $NaCl$ present in $1$ L of solution.
Hence, the molarity of $NaCl$ is $\frac{2mol}{1L}=2M$