Rate of reaction

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Question 8
Easy

A student investigated how the concentration of dilute nitric acid affects the rate of its reaction with sodium thiosulfate solution using a disappearing cross method.

During the investigation, the student:

  1. Measures 125 cm3125\text{ cm}^3125 cm3 of sodium thiosulfate solution of a fixed concentration into a conical flask.
  2. Places the flask over a paper sheet marked with a black cross.
  3. Adds 15 cm315\text{ cm}^315 cm3 of dilute nitric acid of a specific concentration.
  4. Immediately starts a stopwatch and measures the time taken for the sulfur precipitate to obscure the cross from view.
a.

Explain why a 100 cm3100\text{ cm}^3100 cm3 conical flask is unsuitable to use in this method.

[2]
b.

Identify the independent variable and the dependent variable in this investigation.

[2]
c.

The table below shows the results of the experiment using different concentrations of nitric acid:

Concentration of nitric acid (mol/dm3\text{mol/dm}^3mol/dm3)Time taken for cross to disappear (seconds)
0.2180
0.492
0.661
0.845

Which concentration of nitric acid has the highest rate of reaction? Explain how the data shows this.

[2]

Rate of reaction Questions

  1. GCSE
  2. /Chemistry
  3. /Rate of reaction