Core practical - measuring the production of a gas

Question 1

method: Core practical - measuring the production of a gas (6)

Answer 1

1-Support a gas syringe with a stand, boss and clamp.
2-Using a measuring cylinder, add 50 cm3 of dilute hydrochloric acid to a conical flask.
3-Add 0.4 g of calcium carbonate to the flask. Immediately connect the gas syringe and start a stop clock.
4-Record the time for every 10 cm3 of gas produced.
5-When the reaction is complete, clean the apparatus as directed by the teacher.
6-Repeat steps 1 to 5 with different concentrations of hydrochloric acid.

Question 2

what would you be able to see when Sodium thiosulfate solution reacts with dilute hydrochloric acid?

Answer 2

The sulfur forms a cloudy yellow-white precipitate during the reaction

Question 3

method: Core practical - observing colour changes (7)

Answer 3

1-Using a measuring cylinder, add 50 cm3 of dilute sodium thiosulfate solution to a conical flask.
2-Place the conical flask on a piece of paper with a black cross drawn on it.
3-Using a different measuring cylinder, add 10 cm3 of dilute hydrochloric acid to the conical flask. Immediately swirl the flask to mix its contents and start a stop clock.
4-Measure and record the temperature of the reaction mixture.
5-Look down through the reaction mixture. When the cross is no longer visible, record the time on the stop clock.
6-Measure and record the temperature of the reaction mixture, and clean the apparatus as directed by the teacher.
7-Repeat steps 1 to 6 with different starting temperatures of sodium thiosulfate solution.

Question 4

Suggest a reason why the same person should look at the black cross each time. (2)

Answer 4

-different people may decide that they cannot see the cross at different amounts of cloudiness,
-leading to errors in deciding when to take the reaction time.