Question

$25.3$ g of sodium carbonate, $N{a}_{2}C{O}_3$ is dissolved in enough water to make $250$ mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, $N{a}^{+}$ and carbonate ions, $C{O}_3^{2-}$ are: (Molar mass of $N{a}_{2}C{O}_3=106$ g$mo{l}^{-1}$)

• A. $0.955$M and $1.910$M
• B. $1.910$M and $0.955$M
• C. $1.90$M and $1.910$M
• D. $0.477$M and $0.477$M

Answer 1

The correct option is B $1.910$M and $0.955$M

$N{a}_{2}C{O}_3\to 2N{a}^{+}+C{O}_3^{2-}$

Molar mass of $N{a}_{2}C{O}_3=2\times 23+12+16\times 3$

$106gmol-1$

mole of $N{a}_{2}C{O}_3=\frac{25.3}{106}=0.23868$

Mole of $N{a}^{+}$ formed =$0.23868\times 2=0.47736$

concentration of $N{a}^{+},\left[N{a}^{+}\right]=\frac{0.47736}{250ml\times {10}^{-3}}$

$1910M$

Mole of $C{O}_3^{2-}$ formed =$0.23868$

Concentration $\left[C{O}_3^{2-}\right]=\frac{0.23868}{250l\times {10}^{-3}}$

$0.955M$