Question

Prepare 250 cm3 2M NAOH: molar mass M = 40g/mol. calculate substance mass​

Answer 1

Answer: The mass of the substance is 20 g

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

$Molarity=\frac{n\times 1000}{V_s}$

where,

n = moles of solute

$V_s$ = volume of solution in ml  = 250 ml   $(1cm^3=1ml)$

moles of $NaOH$ = $\frac{\text {given mass}}{\text {Molar mass}}=\frac{xg}{40g/mol}$

Now put all the given values in the formula of molality, we get

$2=\frac{x\times 1000}{40\times 250}$

$x=20g$

Therefore, the mass of the substance is 20 g