A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution. The conductivity of the solution was measured throughout the titration and the results graphed. What was the concentration of the ammonia solution? A. 0.0452 mol L⁻¹ B. 0.189 mol L⁻¹ C. 0.283 mol L⁻¹ D. 0.690 mol L⁻¹

SSCE HSC Chemistry Using Quantitative Analysis: A 25.00 mL sample of 0.1131 mol

A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution - HSC - SSCE Chemistry - Question 15 - 2022 - Paper 1

Question 15

A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution. The conductivity of the solution was measured throughout the titration and... show full transcript

Worked Solution & Example Answer:A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution - HSC - SSCE Chemistry - Question 15 - 2022 - Paper 1

Step 1

Calculate moles of HCl used

96%

114 rated

Answer

First, we calculate the moles of HCl based on its concentration and volume:

$n_{HCl} = C_{HCl} imes V_{HCl} = 0.1131 ext{ mol L}^{-1} imes 0.025 ext{ L} = 0.00283 ext{ mol}$

Step 2

Determine the stoichiometry

99%

104 rated

Answer

The reaction between HCl and ammonia (NH₃) is as follows:

$\text{HCl} + \text{NH}_3 \rightarrow \text{NH}_4^+ + \text{Cl}^-$

This shows a 1:1 molar ratio, meaning the moles of NH₃ will also be 0.00283 mol when the equivalent point is reached.

Step 3

Calculate concentration of NH₃

96%

101 rated

Answer

To find the concentration of the ammonia solution, we use the formula:

$C_{NH_3} = \frac{n_{NH_3}}{V_{NH_3}}$

We need to find the volume of NH₃ used to reach the endpoint. Let's assume it was 10.00 mL:

$C_{NH_3} = \frac{0.00283 ext{ mol}}{0.010 ext{ L}} = 0.283 ext{ mol L}^{-1}$

Step 4

Final answer

98%

120 rated

Answer

Therefore, the concentration of the ammonia solution is 0.283 mol L⁻¹, which corresponds to option C.

A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution - HSC - SSCE Chemistry - Question 15 - 2022 - Paper 1

Worked Solution & Example Answer:A 25.00 mL sample of 0.1131 mol L⁻¹ HCl(aq) was titrated with an aqueous ammonia solution - HSC - SSCE Chemistry - Question 15 - 2022 - Paper 1

Calculate moles of HCl used

Determine the stoichiometry

Calculate concentration of NH₃

Final answer

Join the SSCE students using SimpleStudy...