A student investigated the effect of temperature on the speed of reaction between hydrochloric acid and aqueous sodium thiosulfate. When these chemicals react they form a precipitate, which makes the solution go cloudy. The formation of this precipitate can be used to show how fast the reaction proceeds, using the set up shown below.
Five experiments were carried out.
Experiment 1
By using a measuring cylinder 50 cm3 of aqueous sodium thiosulfate was poured into a flask. The temperature of the solution was measured. The conical flask was placed on the printed text. 10 cm3 of hydrochloric acid was added to the flask and the timer started. The time taken for the printed text to disappear from view was recorded in the table. The final temperature of the mixture was measured.
Experiment 2
50 cm3 of aqueous sodium thiosulfate was poured into a conical flask. The solution was heated until the temperature was about 30 °C. The temperature of the solution was measured. 10 cm3 of hydrochloric acid was added to the flask and Experiment 1 was repeated.
The final temperature of the liquid was measured.
Experiment 3
Experiment 2 was repeated but the sodium thiosulfate solution was heated to about 40 °C before adding the hydrochloric acid.
The initial and final temperatures were measured.
Experiment 4
Experiment 2 was repeated but the sodium thiosulfate solution was heated to about 50 °C before adding the hydrochloric acid.
The initial and final temperatures were measured.
Experiment 5
Experiment 2 was repeated but the sodium thiosulfate solution was heated to about 60 °C before adding the hydrochloric acid.
The initial and final temperatures were measured. Use the thermometer diagrams to record all of the initial and final temperatures in the table.
Complete the table of results to show the average temperatures.
Table 1