Acids, alkalis and titrations

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Question 12

A student performed a titration to find the concentration of a solution of sulfuric acid, $H2SO4\text{H}_2\text{SO}_4$ , using a standard solution of sodium hydroxide, $NaOH\text{NaOH}$ .

The student repeated the titration of sulfuric acid solution with the sodium hydroxide solution and recorded these results:

Run	1	2	3	4
Burette reading after adding alkali / $cm3\text{cm}^3$	23.90	22.20	23.30	22.65
Burette reading before adding alkali / $cm3\text{cm}^3$	1.25	0.90	1.45	0.70
Volume of alkali added / $cm3\text{cm}^3$	22.65	21.30	21.85	21.95

The average (mean) volume of sodium hydroxide added should be calculated using only concordant results. Concordant results are those volumes that differ from each other by $cm30.10\text{ cm}^3$ or less.

Identify the concordant results by stating which runs should be selected.

[1]

Calculate the average (mean) volume of sodium hydroxide added using your selected results.

[1]

The student used the same method to find the concentration of another sulfuric acid solution. The equation for the reaction is:

\text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}

These are the student's experimental results:

Volume of sulfuric acid solution: $cm320.0\text{ cm}^3$
Volume of sodium hydroxide solution added: $cm318.60\text{ cm}^3$
Concentration of sodium hydroxide solution: $mol/dm30.150\text{ mol/dm}^3$

The student used these results to calculate the concentration of the sulfuric acid solution:

Step 1: $mol\text{amount of NaOH} = \frac{0.150 \times 18.60}{100} = 0.0279\text{ mol}$
Step 2: $mol\text{amount of H}_2\text{SO}_4 = 0.0279 \times 2 = 0.0558\text{ mol}$
Step 3: $mol/dm3\text{concentration of H}_2\text{SO}_4 = \frac{0.0558}{18.60} \times 1000 = 3.00\text{ mol/dm}^3$

There is one mistake in each step of the calculation. What correction should the student make in Step 1?

[1]

What correction should the student make in Step 2?

[1]

What correction should the student make in Step 3?

[1]

Acids, alkalis and titrations

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Question 12

A student performed a titration to find the concentration of a solution of sulfuric acid, $H2SO4\text{H}_2\text{SO}_4$ , using a standard solution of sodium hydroxide, $NaOH\text{NaOH}$ .

The student repeated the titration of sulfuric acid solution with the sodium hydroxide solution and recorded these results:

Run	1	2	3	4
Burette reading after adding alkali / $cm3\text{cm}^3$	23.90	22.20	23.30	22.65
Burette reading before adding alkali / $cm3\text{cm}^3$	1.25	0.90	1.45	0.70
Volume of alkali added / $cm3\text{cm}^3$	22.65	21.30	21.85	21.95

Identify the concordant results by stating which runs should be selected.

[1]

Calculate the average (mean) volume of sodium hydroxide added using your selected results.

[1]

The student used the same method to find the concentration of another sulfuric acid solution. The equation for the reaction is:

\text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}

These are the student's experimental results:

Volume of sulfuric acid solution: $cm320.0\text{ cm}^3$
Volume of sodium hydroxide solution added: $cm318.60\text{ cm}^3$
Concentration of sodium hydroxide solution: $mol/dm30.150\text{ mol/dm}^3$

The student used these results to calculate the concentration of the sulfuric acid solution:

Step 1: $mol\text{amount of NaOH} = \frac{0.150 \times 18.60}{100} = 0.0279\text{ mol}$
Step 2: $mol\text{amount of H}_2\text{SO}_4 = 0.0279 \times 2 = 0.0558\text{ mol}$
Step 3: $mol/dm3\text{concentration of H}_2\text{SO}_4 = \frac{0.0558}{18.60} \times 1000 = 3.00\text{ mol/dm}^3$

There is one mistake in each step of the calculation. What correction should the student make in Step 1?

[1]

What correction should the student make in Step 2?

[1]

What correction should the student make in Step 3?

[1]

Acids, alkalis and titrations

Question 12

Acids, alkalis and titrations Questions

Acids, alkalis and titrations

Question 12

Acids, alkalis and titrations Questions