4.3 - rates Flashcards
1
Q
disappearing cross experiment (effect of concentration on rate)
A
- put a black cross under a conical flask
- react sodium thiosulphate solution with hydrochloric acid in this flask
- start the timer
- in this reaction, a solid (sulphur) is slowly produced
- after a while you can’t see through the mixture any longer, stop the timer
- rate calculated from: 1/time taken (s
2
Q
what are the variables for the disappearing cross experiment
A
- concentration of the sodium thiosulphate
- time taken for the cross to disappear
- total volume of solution
- concentration of HCl (aq)
- temperature
3
Q
rate is ______ to concentration
A
proportional
4
Q
marble chip experiment
A
- react calcium carbonate (marble) chips with hydrochloric acid in a conical flask
- put a bung on the conical flask with a gas syringe to measure the volume of CO2 (g) released
- have it for a set time (e.g. a minute)
- need to do it with different s.a. of chips and compare (same mass/volume of them though)
5
Q
magnesium and acid experiment
A
- react a magnesium ribbon with hydrochloric acid in a test tube
- magnesium disappears
- measure the time it takes for this to happen
- rate: 1/time taken (s)
- graph isn’t a straight line - rate isn’t proportional to temperature
- doesn’t go through origin - rate isn’t zero at 0°C
6
Q
rate ________ to temperature
A
isn’t proportional
