Question

A 4.00 g mass of NaOH is dissolved in 5.00 mL of water. A 4.00-mL aliquot of this solution is then diluted to exactly 500 mL of solution using distilled water. What is molar concentration of NaOH in the final diluted solution?

Answer 1

Answer: The molar concentration of NaOH in the final diluted solution is 0.056 M

Explanation:

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

Given mass of NaOH = 4.00 g

Molar mass of NaOH = 40 g/mol

Volume of solution = 5.00 mL

Putting values in above equation, we get:

$\text{Molarity of NaOH solution}=\frac{1.40\times 1000}{40\times 5}\\\\\text{Molarity of NaOH}=7M$

To calculate the molarity of the diluted solution, we use the equation:

$M_1V_1=M_2V_2$

where,

$M_1\text{ and }V_1$ are the molarity and volume of the concentrated NaOH solution

$M_2\text{ and }V_2$ are the molarity and volume of diluted NaOH solution

We are given:

$M_1=7M\\V_1=4.00mL\\M_2=?M\\V_2=500mL$

Putting values in above equation, we get:

$7\times 4.00=M_2\times 500\\\\M_2=\frac{7\times 4.00}{500}=0.056M$

Hence, the molar concentration of NaOH in the final diluted solution is 0.056 M