Sodium thiosulfate reacts with dilute hydrochloric acid as shown - AQA - A-Level Chemistry - Question 1 - 2019 - Paper 3
Question 1
Sodium thiosulfate reacts with dilute hydrochloric acid as shown.
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l)
1. Give the simplest ionic equation fo... show full transcript
Worked Solution & Example Answer:Sodium thiosulfate reacts with dilute hydrochloric acid as shown - AQA - A-Level Chemistry - Question 1 - 2019 - Paper 3
Step 1
Give the simplest ionic equation for this reaction.
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State the property of SO2 that causes pollution when it enters rivers.
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Answer
The property of SO2 that causes pollution when it enters rivers is its acidic nature, which can lower the pH of the water, harming aquatic life.
Step 3
Give an equation to show the reaction of SO2 with water.
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Answer
The equation for the reaction of SO2 with water is:
ightarrow ext{H}_2SO_3 (aq) $$
Step 4
Draw a diagram to show the shape of a molecule of H2O. Include any lone pairs of electrons.
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Answer
The diagram of a water molecule (H2O) is as follows:
H
|
O
/
H
There are two lone pairs of electrons on the oxygen atom.
Step 5
State the H-O-H bond angle.
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Answer
The H-O-H bond angle in water is approximately 104.5°.
Step 6
Explain this shape and bond angle.
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Answer
The shape of the water molecule is bent due to the two lone pairs of electrons on the oxygen atom. These lone pairs repel the bond pairs more strongly than the bond pairs repel each other, which reduces the bond angle from the ideal tetrahedral angle of 109.5° to approximately 104.5°.
Step 7
Describe an experiment to investigate the effect of temperature on the initial rate of this reaction.
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Answer
To investigate the effect of temperature on the initial rate of reaction:
Method Outline: Prepare solutions of sodium thiosulfate and hydrochloric acid. Set up several test tubes with equal volumes of sodium thiosulfate. Use different water baths to maintain varying temperatures (e.g., 20°C, 30°C, 40°C, 50°C).
Measure Time: To measure the time taken for sulfur to form, add hydrochloric acid to the sodium thiosulfate solution and start a stopwatch. Record the time until the solution becomes opaque due to sulfur precipitation.
Graphical Results: Present your results in a table showing temperature vs time taken for sulfur to appear.
Expected Graph: You would expect a graph that shows a decrease in time taken (indicating an increase in rate) as temperature increases.
