Question

Suppose you wanted to make an aqueous solution of sodium hydroxide that is 1.8 M. You want to make 250 ml of the solution. How many grams of sodium hydroxide are needed to make this solution? Note which type of calculation you need to perform, and then perform the calculation.

Answer 1

Molarity to moles to mass.

0.250 L (1.8 mol/L) = 0.45 mol NaOH
0.45 mol (39.99 g/mol) = 18.00 g NaOH

How's that?

Answer 2

Answer : The mass of sodium hydroxide is, 18 grams

Explanation : Given,

Molarity of sodium hydroxide = 1.8 M = 1.8 mole/L

Molar mass of sodium hydroxide = 40 g/mole

Volume of solution = 250 ml

Molarity : It is defined as the number of moles of solute present in one liter of solution.

In this question, the solute is sodium hydroxide.

Formula used :

`Molarity=\frac{\text{Mass of solute}* 1000}{\text{Molar mass of solute}* \text{volume of solution in ml}}`

Now put all the given values in this formula, we get the mass of sodium hydroxide.

`1.8mole/L=\frac{\text{Mass of solute}* 1000}{40g/mole* 250ml}`

`\text{Mass of solute}=18g`

Therefore, the mass of sodium hydroxide is, 18 grams