Rate of reaction

Easy

A student investigated the rate of the reaction of sodium thiosulfate solution with dilute hydrochloric acid using the disappearing cross experiment.

During the method, the student:

Measures $cm370\text{ cm}^3$ of sodium thiosulfate solution into a conical flask placed over a paper sheet with a pencil cross.
Adds $cm310\text{ cm}^3$ of dilute hydrochloric acid.
Measures the time taken for the cross to be obscured by the sulfur precipitate.

Explain why a $cm350\text{ cm}^3$ conical flask is unsuitable to use in this method.

[2]

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

[2]

The table below shows the results of the experiment:

Concentration of sodium thiosulfate ( $g/dm3\text{g/dm}^3$ )	Time taken for cross to disappear (seconds)
6	150
12	75
18	50
24	38

Which concentration of sodium thiosulfate solution has the highest rate of reaction? Explain how the data shows this.

[2]

Rate of reaction Questions