Question

How are 0.50 mol Na₂CO₃ and 0.50 M Na₂CO₃ different?

Answer 1

1. 0.50 mol Na₂CO₃

• Refers to the amount of substance only, not solution.
• It means: \[ n = 0.50 \ \text{mol of Na}_2\text{CO}_3 \]
• No information is given about the volume of solution or whether it is dissolved at all.

2. 0.50 M Na₂CO₃

• Molarity (M) is defined as: \[ M = \frac{\text{moles of solute}}{\text{volume of solution in litres}} \]
• 0.50 M Na₂CO₃ means there are 0.50 mol of Na₂CO₃ in 1.00 L of solution.
• So, it describes a concentration of a solution, not just the amount of solute.

3. Key Contrast (LaTeX Summary)

\[ 0.50 \ \text{mol Na}_2\text{CO}_3 \Rightarrow \text{fixed amount, no volume specified} \] \[ 0.50 \ \text{M Na}_2\text{CO}_3 \Rightarrow 0.50 \ \text{mol in 1.00 L of solution (a concentration)} \]