Question

How many grams of 50 wt% NaOH (FM 40.00) should be diluted to 1.00 L to make 0.10 M NaOH? (Answer with two digits.)

Answer 1

Molarity is one of a way to express concentration of the solution and it is generally expressed as number of moles of solute per litre of the solution.

And number of mole is given by,

Given,

Molarity of the soluion = 0.1 M

Volume of the solution = 1.00 L

First Step:

Calculation on number of moles of NaOH present in 0.01 M solution

Second Step:

Calculation of amount of NaOH in grams from no. of mole

Number of mole of NaOH = 0.1

Molecular mass of NaOH = 40

hird Step:

Calculation of amount of 50% NaOH required to make 0.01 M solution

Amount of NaOH in g required to make 1.0 L of 0.1 M = 4.0 g

since, initially 50% by weight NaOH is taken.

Wt % is the amount of substance present in 100 g of the solution.

50% by weight NaOH means 50 g is present in 100 g of solution.

By using unitary method,

50 g NaOH is present in 100 g of the NaOH sample

1 g NaOH will be present in 100/50 g of the NaOH sample

4 g NaOH will be present in 100/50*4 = 8.0 g of the NaOH sample

Amount of 50 wt% NaOH required = 8.0 g