In an experiment, sulfuric acid reacted with different volumes of sodium thiosulfate in water. A yellow precipitate was formed during the reaction. A cross drawn at the base of each flask became gradually invisible due the formation of this yellow precipitate. The time taken for the cross to become invisible was recorded. A partial record of the experiment is shown. Experimental Record Flask Volume of H2SO4 Volume of Sodium Thiosulfate Volume of Water Time 1 5 mL 50 mL 0 mL 19 seconds 2 5 mL 40 mL 10 mL 3 5 mL 30 mL 20 mL 4 5 mL 20 mL 30 mL Based on your knowledge of factors that affect the rates of chemical reactions, predict the trend in the last column of the experimental record. Use complete sentences to explain the trend you predicted. You do not have to determine exact values for time; just describe the trend you would expect (increase or decrease) and why it occurs.

Question

Chemistry

Murphy

17 November, 08:40

In an experiment, sulfuric acid reacted with different volumes of sodium thiosulfate in water. A yellow precipitate was formed during the reaction. A cross drawn at the base of each flask became gradually invisible due the formation of this yellow precipitate. The time taken for the cross to become invisible was recorded. A partial record of the experiment is shown. Experimental Record Flask Volume of H2SO4 Volume of Sodium Thiosulfate Volume of Water Time 1 5 mL 50 mL 0 mL 19 seconds 2 5 mL 40 mL 10 mL 3 5 mL 30 mL 20 mL 4 5 mL 20 mL 30 mL Based on your knowledge of factors that affect the rates of chemical reactions, predict the trend in the last column of the experimental record. Use complete sentences to explain the trend you predicted. You do not have to determine exact values for time; just describe the trend you would expect (increase or decrease) and why it occurs.

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Answers (1)

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Celia Schultz · Answer 1

Answer: The time needed for the reaction will increase. A cross drawn at the base of each flask became gradually invisible due to the formation of this yellow precipitate. The time needed for the reaction will increase from flask 1 to flask 5.

Explanation:

Rate of chemical reaction α [reactants].

If we suppose here that the reaction is a second-order reaction which means that the reaction depends on the concentration of both H₂SO₄ and thiosulfate.

∴ Rate of the reaction = k[H₂SO₄][thiosulfate].

where k is the rate constant of the reaction.

Here, the concentration of H₂SO₄ is constant, since we use a constant amount of it.

The concentration of thiosulfate decreased from flask 1 to flask 5 as the amount of added thiosulfate decreased.

Rate α [thiosulfate]

As the concentration of the thiosulfate decreased, the rate of the reaction will decrease.

The rate of the reaction is the change in the concentration of the reactants per time.

Rate of the reaction = - Δ[thiosulfate]/Δt.

As we mentioned that the concentration of thiosulfate decreased since the rate of the reaction will decrease.

The rate of the reaction is inversely proportional to time (rate α 1/t).