Rates of Reaction RP

Question 1

Measuring volume of gas produced Independent variable and dependent variable

Answer 1

IV: temperature or concentration
DV: volume of gas produced

Question 2

Measuring volume of gas method

Answer 2

1. get a conical flask, a bung, a tube and a gas syringe - connect tube and gas syringe and bung.
2. measure out 50cm3 of 1 mol/dm3 of hydrochloric acid using a measuring cylinder, and pour into a conical flask
3. add a 4cm strip of magnesium ribbon
4. quickly place the bung on top.
5. record the volume of gas produced every 10 seconds - using gas syringe and a stopwatch
6. repeat using a different concentration of hydrochloric acid
7. plot a graph of results

Question 3

Graph to show how rate depends on concentration

Describe the results

Answer 3

The curve finishes at the same point for both acids because the same amount of Magnesium was used

The steeper the curve, the higher the rate of reaction
The shallower the curve the lower the rate of reaction

The higher the concentration of acid, the higher the rate of reaction

Question 4

Measuring rate of reaction using turbidity

Independent and dependent variables

Answer 4

IV: temperature or concentration of sodium thiosulfate in g/dm3
DV: time taken for cross to disappear in seconds

Question 5

Measuring rate of reaction using turbidity
Method

Answer 5

1. measure 50 cm3 of sodium thiosulfate with a measuring cylinder and pour into a conical flask
2. place the conical flask on a piece of paper with a black cross on it
3. using a different measuring cylinder, measure 10cm3 of dilute hydrochloric acid to the conical flask.
4. swirl to mix the contents inside the flask and start a stop watch
5. look down through the reaction mixture, and stop the stop watch when the black cross can no longer be seen.
6. record down the time it takes for the cross to disappear.
7. repeat investigation twice so you get three results and calculate a mean
8. repeat steps 1-7 for different concentrations of sodium thiosulfate

Question 6

Control variables for the cross method

Answer 6

Size of cross
Thickness of cross
Darkness of cross
volume of hydrochloric acid
Temperature - if you aren’t changing that

Question 7

sources of error for the cross method

Answer 7

Judgement when cross disappears is subjective as it depends on the person making a judgement

Use a light sensor to judge when cross disappears

Question 8

Which word describes investigations performed by different students, which give a similar apttern of results

Answer 8

Reproducible

Question 9

Why does time taken for the cross to become no longer visible decrease when concentration of sodium thiosulfate increases

Answer 9

More particles in a fixed volume, so frequency of successful collisions with acid particles increase