Calculate the molarity of a solution prepared by dissolving 8.00 g of sodium carbonate (Na₂CO₃, M = 105.99 g·mol⁻¹) in enough water to make 500.0 mL of solution at 25 °C.
Answer
M = 0.151 mol·L⁻¹
The correct answer is M = 0.151 mol·L⁻¹ — Molarity M = n / V = 0.0755 mol / 0.5000 L = 0.151 mol·L⁻¹.
Step-by-step solution
- Find the amount of substance of Na₂CO₃: n = mass / molar mass = 8.00 g / 105.99 g·mol⁻¹ = 0.0755 mol.
- Convert the solution volume to litres: V = 500.0 mL = 0.5000 L.
- Molarity M = n / V = 0.0755 mol / 0.5000 L = 0.151 mol·L⁻¹.
Common mistake: Using 500 mL directly as litres instead of converting to 0.500 L
Concept tested: Molarity calculation
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