Question

How many grams of solid NaOH are required to prepare a 400ml of a 5N solution? show your work!

Answer 1

Answer: The mass of solid NaOH required is 80 g

Step-by-step explanation:

Equivalent weight is calculated by dividing the molecular weight by n factor. The equation used is:

`\text{Equivalent weight}=\frac{\text{Molecular weight}}{n}`

where,

n = acidity for bases = 1 (For NaOH)

Molar mass of NaOH = 40 g/mol

Putting values in above equation, we get:

`\text{Equivalent weight}=(40g/mol)/(1eq/mol)=40g/eq`

Normality is defined as the umber of gram equivalents dissolved per liter of the solution.

Mathematically,

`\text{Normality of solution}=\frac{\text{Number of gram equivalents} * 1000}{\text{Volume of solution (in mL)}}`

Or,

`\text{Normality of solution}=\frac{\text{Given mass}* 1000}{\text{Equivalent mass}* \text{Volume of solution (in mL)}}` ......(1)

We are given:

Given mass of NaOH = ?

Equivalent mass of NaOH = 40 g/eq

Volume of solution = 400 mL

Normality of solution = 5 eq/L

Putting values in equation 1, we get:

`5eq/L=\frac{\text{Mass of NaOH}* 1000}{40g/eq* 400mL}\\\\\text{Mass of NaOH}=80g`

Hence, the mass of solid NaOH required is 80 g