Question

0.02 g of mono basic acid requires 8cm^3 of 0.04moldm^3 sodium hydroxide for complete reaction. Molecular mass of acid is?

Answer 1

Step 1: Calculate moles of NaOH used;

We have 0.04 moles in 1dm³

1dm^3=1000cm³

if 0.04moles are in 1000cm³

How many moles will be in the 8cm³?

$Moles of NaOH=\dfrac{0.04molx8cm^3}{1000cm^3} = 0.00032mol$

Step 2: Balanced equation for the reaction;

HA_(aq) + NaOH_(aq) $\to$ NaA_(aq) + H₂O_(l)

Mole ratio=1:1

Thus moles of the acid$=\dfrac{1}{1}x0.00032=0.00032moles$

Step 3: Calculate Molecular mass from moles of acid

$Molecular mass=\dfrac{mass}{moles} = \dfrac{0.02g}{0.00032mol} = 62.5g/mol$