Question

What mass of HNO3 containing 10% W/W of acid will be required to dissolve 2.5g of CaCO3

Answer 1

First we write the balanced equation for the reaction as;

2HNO₃ + CaCO₃ $\to$ Ca (NO₃)₂ + H₂O + CO₂

Moles of CaCO3 in 2.5g $=$ $\dfrac{mass}{Molar mass}=\dfrac{2.5g}{100.0869g/mol}=0.024978mol$

Moles of HNO3 required;

Mole ratios of HNO₃:CaCO₃ = 2:1

Moles of HNO3 $=\dfrac{2}{1}xmoles of CaCO3$

$=\dfrac{2}{1}x0.024978 = 0.049957mol$

Concentration of acid = 10% w/w

That means 10g of HNO3 in 100g of solution

That is $\dfrac{10g}{63.01g/mo} moles$ of HNO3 in 100g of solution

= 0.1587 moles of HNO3 in 100g of solution

Now, If 0.1587 moles are in 100g of solution;

0.049957 moles will be in?

$=\dfrac{0.049957mol x 100g}{0.1587mol}$

$=$ 31.479 g of 10% w/w of HNO₃