Question

500 ml of 0.90M CH3COOH solution is mixed with 600 ml 12% w/v CH3COOH solution then calculate the final molarity of solution.

Answer 1

1.5 M

Answer 2

To calculate the final molarity of the solution, we need to determine the total moles of CH3COOH and the total volume of the mixed solution.

1. Moles of CH3COOH from the first solution:

• Volume (V1) = 500 ml = 0.5 L
• Molarity (M1) = 0.90 M
• Moles of CH3COOH (n1) = M1 × V1 = 0.90 mol/L × 0.5 L = 0.45 moles

2. Moles of CH3COOH from the second solution:

• Volume (V2) = 600 ml
• Concentration = 12% w/v (weight/volume)
  • This means there are 12 g of CH3COOH in every 100 ml of solution.
  • Mass of CH3COOH in 600 ml = $\left( \frac{12 \text{ g}}{100 \text{ ml}} \right) \times 600 \text{ ml} = 72 \text{ g}$
• Molar mass of CH3COOH (acetic acid) = (2 × Atomic mass of C) + (4 × Atomic mass of H) + (2 × Atomic mass of O)
  • = (2 × 12.01) + (4 × 1.008) + (2 × 15.999) $\approx$ 60.05 g/mol. For practical calculations, 60 g/mol is commonly used.
  • Let's use 60 g/mol.
• Moles of CH3COOH (n2) = $\frac{\text{Mass}}{\text{Molar mass}} = \frac{72 \text{ g}}{60 \text{ g/mol}} = 1.2 \text{ moles}$

3. Total moles of CH3COOH:

• Total moles (n_total) = n1 + n2 = 0.45 moles + 1.2 moles = 1.65 moles

4. Total volume of the mixed solution:

• Assuming volumes are additive,
• Total volume (V_total) = V1 + V2 = 500 ml + 600 ml = 1100 ml = 1.1 L

5. Final Molarity of the solution:

• Final Molarity (M_final) = $\frac{\text{Total moles}}{\text{Total volume (in Liters)}} = \frac{n_{\text{total}}}{V_{\text{total}}}$
• M_final = $\frac{1.65 \text{ moles}}{1.1 \text{ L}} = 1.5 \text{ M}$

The final molarity of the solution is 1.5 M.

Explanation of the solution:

1. Calculate moles of CH3COOH from the first solution using Molarity = moles/volume.
2. Calculate moles of CH3COOH from the second solution by first converting %w/v to mass, then mass to moles using molar mass of CH3COOH (60 g/mol).
3. Sum the moles from both solutions to get total moles of CH3COOH.
4. Sum the volumes of both solutions to get the total volume (assuming volumes are additive).
5. Divide total moles by total volume (in Liters) to find the final molarity.