Question

The mass of sulphuric acid needed for dissolving $3g$ magnesium carbonate is:

• A. $3.5g$
• B. $7g$
• C. $1.7g$
• D. $17.0g$

Answer 1

The correct option is A $3.5g$

Molar mass of $MgC{O}_3$ is $=84.3g$

$\therefore$ 3g of $MgC{O}_3=3/84.3mol=0.036mol$

The balanced equation is:

$H_{2}S{O}_4+MgC{O}_3\to MgS{O}_4+H_{2}C{O}_3$

It is evident that one mole of sulphuric acid is required to dissolve i mole $MgC{O}_3$

$\therefore$ 0.036 mole of sulphuric acid is required to dissolve 0.036 mole of $MgC{O}_3$

or

$0.036\times 98.1=35.5g$ of sulphuric acid is required.