Question

$25.3 \, g$ of sodium carbonate, $Na_2CO_3$ is dissolved in enough water to make $250 \, mL$ of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, $Na^+$ and carbonate ions,$CO^{2-}_3$ are respectively (Molar mass of $Na_2CO_3 = 106 \, g \, mol^{-1}$)

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

Answer 1

Answer: (C)

1.910 M and 0.955 M

Answer 2

Molarity = $\frac{25.3 \times 1000}{106 \times 250} = 0.955 \, M$
${ Na_2 CO_3 -> 2Na^+ + CO^{-2}_3}$
$= 2 \times 0.955 \, \, 0.955 \, M$
$= 1.910 \, M$