Question

The amount of Na$_2$CO$_3$ to prepare 500 ml 0.2 M solution is –

• A. 1.53 g
• B. 3.06 g
• C. 10.6 g
• D. 5.3 g

Hint:

Always remember: Moles = Molarity $\times$ Volume (L), and Mass = Moles $\times$ Molar Mass.

Answer 1

The Correct Option is C

Step 1: Recall the formula.
The mass of solute required is calculated by: \[ \text{Mass (g)} = Molarity \times Volume(L) \times Molar \, Mass \]

Step 2: Write known values.
- Molarity (M) = 0.2 M
- Volume (V) = 500 ml = 0.5 L
- Molar mass of Na$_2$CO$_3$ = (23$\times$2) + 12 + (16$\times$3) = 46 + 12 + 48 = 106 g/mol

Step 3: Calculate mass.
\[ \text{Mass} = 0.2 \times 0.5 \times 106 \] \[ \text{Mass} = 10.6 \, g \] Step 4: Final Answer.
Thus, to prepare 500 ml of 0.2 M Na$_2$CO$_3$ solution, 10.6 g of Na$_2$CO$_3$ is required.
\[ \boxed{10.6 \, g} \]