Question

A student needed to make 100.0 mL of 0.20M NaOH solution. How many grams of sodium hydroxide does the student need to weigh out

Answer 1

Answer:

0.8 g

Explanation:

The molarity of a solution is calculated with the following formula:

$M=\frac{n}{V}$

where:

n is the number of moles of the solute

V is the volume of the solution

In this problem we have:

V = 100.0 mL = 0.1 L is the volume of the solution

M = 0.20 is the molarity

So the number of moles of NaOH in the solution must be

$n=MV=(0.20)(0.1)=0.02 mol$

The molar mass of NaOH is

$M_m = 40 g/mol$

Therefore, the mass of NaOH needed in the solution is:

$m=nM_m = (0.02)(40)=0.8 g$