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 Concentration and Molarity: 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 the moles of HCl used

96%

114 rated

Answer

First, convert the volume of HCl from mL to L:

$25.00 ext{ mL} = 0.025 ext{ L}$

Next, calculate the moles of HCl using its concentration:

$ext{Moles of HCl} = 0.1131 ext{ mol L}^{-1} imes 0.025 ext{ L} = 0.0028275 ext{ mol}$

Step 2

Determine the stoichiometry of the reaction

99%

104 rated

Answer

The balanced reaction between HCl and NH₃ can be described as:

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

This shows a 1:1 molar ratio, meaning 0.0028275 moles of NH₃ will completely react with 0.0028275 moles of HCl.

Step 3

Find the concentration of ammonia solution

96%

101 rated

Answer

If 'V' represents the volume of ammonia added (which we can assume is provided by the graph), the moles of NH₃ can be related to its concentration:

$ext{Concentration of NH}_3 = rac{ ext{moles of NH}_3}{ ext{Volume of NH}_3}$

Assuming we used 10 mL of NH₃ solution in the titration (you will need to refer to the graph for accurate volume):

$ext{Concentration of NH}_3 = rac{0.0028275 ext{ mol}}{0.010 ext{ L}} = 0.283 ext{ mol L}^{-1}$

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 the moles of HCl used

Determine the stoichiometry of the reaction

Find the concentration of ammonia solution

Join the SSCE students using SimpleStudy...