Question

In analyzing the crude fiber content of a particular plant sample, 0.313N NaOH solution is required.

A. What is the mass of NaOH pellets needed to prepare 500ml of the solution? 

B. What is the M of the solution? (MW NaOH: 40g/mol)

Answer 1

A. Sodium hydroxide 0.313 mol/l (0.313 N) 

Then

$$0.313\ mol/l\cdot(0.5\ l)=0.1565\ mol$$

$$22.990+15.999+1.008=39.997$$

Molar Mass of NaOH is $39.997\ g/mol$.

The mass of NaOH pellets needed to prepare 500ml of the solution is

$$0.1565\ mol \cdot (39.997\ g/mol)=6.260 \ g$$

B.

$$Molarity =M=\dfrac{\text{moles of solute}}{\text{liters of soln}}$$

$$M=\dfrac{0.1565\ mol}{0.5\ l}=0.313\ mol/l$$