Question

20gram naoh dissolved in100g solution find the molality

Answer 1

Given -

Mass of NaOH = 20g

Mass of water = 100g

To find -

Molality

Formula used -

• Number of mole = mass ÷ molar mass
• Molality = number of mole of solute ÷ mass of solvent in Kg

Solution -

Molar mass of NaOH = 40g/mol

Moles of NaOH = 20 ÷ 40

Moles of NaOH = 0.5mol

Molality = number of mole of NaOH ÷ mass of water in kg

$\sf \implies\: Molality \:=\: \dfrac{0.5}{ \dfrac{100}{1000} }m \\ \\ \\ \sf \implies\: Molality \:=\: 0.5 \times \frac{1000}{100}m \\ \\ \sf \implies\: Molality \:=\:0.5 \times 10m \\ \\ \sf \implies\: Molality \:=\:5m$

ANSWER - 5m