Chenistry Paper Two

Question 1

Practical for rate of reaction concentration

Answer 1

1.)Measure 50 cm3 of Na2S2O3 solution into a flask
Measure 5 cm3 of dilute HCl into a measuring cylinder
2.)Draw a dark cross on a piece of white paper and put it underneath the flask
3.)Add the acid into the flask and immediately start the stopwatch
4.)Solid sulfur is formed which precipitates in solution, turning cloudy
5.) stop timing when cross can no longer be seen

Question 2

Practical rate of reaction for volume of gas rate of reaction

Answer 2

Magnesium and sulfuric acid will react immediately so the flask must be connected to the gas syringe straight after adding the magnesium to avoid gas escaping

1.)Measure 50 cm3 of 1.0 mol/dm3 sulfuric acid solution into a flask
2.)Add the magnesium ribbon to the flask and connect it to the gas collection equipment
3.)Start the stopwatch and record the volume of gas every 10 seconds
When the reaction is complete, repeat using 1.5 mol/dm3 sulfuric acid

Question 3

Potable water

Answer 3

1.)Use the universal indicator paper to determine the pH of the water sample

2.)Accurately weigh an empty evaporating basin to two decimal places
3.)Add 25 cm3 of water sample A into the evaporating basin
4.)Heat the evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the majority of water has evaporated
6.)Leave for the remaining water to evaporate off
7.)Weigh the cooled evaporating basin again and calculate the mass of the solids that were dissolved in the water.