Question

The weight of $NaHC{O}_3$ that can give the same weight of $C{O}_2$ which can be prepared from 12.5 g of limestone is:

• A. 21 g
• B. 10 g
• C. 84 g
• D. 11 g

Answer 1

The correct option is A 21 g

$2NaHC{O}_3\to N{a}_{2}C{O}_3+H_{2}O+C{O}_2\uparrow$
$CaC{O}_3\to CaO+C{O}_2$
12.5 g of limestone ($CaC{O}_3$ molar mass 100 g/mol) $=\frac{12.5g}{100g/mol}=0.125mol$
0.125 mole limestone will give 0.125 moles $C{O}_2$.
0.125 moles of $C{O}_2$ can be obtained from $2\times 0.125=0.25$ moles $NaHC{O}_3$
The molar mass of $NaHC{O}_3=84$ g/mol.
0.25 moles $NaHC{O}_3=0.25mol\times 84g/mol=21g$