Question 40 of 50beginner🔧 ApplyNumerical2 marks

Calculate the amount of benzoic acid (C6H5COOH) required for preparing 250 mL of 0.15 M solution in methanol.

Correct Answer

4.575 g of benzoic acid is required.

Exercise: EXERCISES | Q: 1.30 | (Page 29)
For More Understanding

Explanation

This is a straightforward molarity calculation. The molarity formula relates moles of solute to the volume of solution. First, calculate the molar mass of benzoic acid, then use the molarity formula to find moles, and finally convert moles to mass.

Solution Steps

  1. Step 1: Calculate molar mass of benzoic acid (C₆H₅COOH) Molar mass = (7×127 \times 12) + (6×16 \times 1) + (2×162 \times 16) = 84 + 6 + 32 = 122 g mol⁻¹

  2. Step 2: Calculate moles of benzoic acid required Molarity = Moles of solute / Volume of solution (in L) Moles = Molarity × Volume = 0.15 mol L⁻¹ × 0.250 L = 0.0375 mol

  3. Step 3: Calculate mass of benzoic acid Mass = Moles × Molar mass = 0.0375 mol × 122 g mol⁻¹ = 4.575 g

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