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Required practical 5: Investigating effect of…
Required practical 5:
Investigating effect of concentration on rate of reaction
Evaluation
Use particle theory to explain the description
If it is appropriate, give a more detailed description
e.g. as the temperature increases, the time taken for the cross to disappear decreases until 50 oC when the time for the cross to disappear remains at 5 seconds
Describe what the graph shows
e.g. as the temperature increases, the time taken for the cross to disappear decreases
Draw a smooth curved line of best fit
Plot a line graph of the results
y-axis = mean time taken for the cross to disappear in seconds
x-axis = sodium thiosulfate concentration in g/dm3
Calculate the mean time for each of the thiosulfate concentrations and record it in the final column
Do not include anomalous values in your calculations
Results
Record your results for each test carefully in a suitable table like the one below:
Practical Tip
To avoid the reaction starting before the chemicals are mixed in steps 6 and 7:
Wash / rinse the conical flask thoroughly between experiments
Make sure that you use the 25 cm3 measuring cylinder for the sodium thiosulfate and the 10 cm3 measuring cylinder for the hydrochloric acid
Method:
Measure 50 cm3 of Na2S2O3 solution into the conical flask
Place the white paper with cross marked on it underneath the conical flask
Measure 10 cm3 of dilute HCl into a measuring cylinder
Add the hydrochloric acid into the flask and immediately start the stopwatch
Look down at the cross and stop the timing when the cross can no longer be seen
Record the time, in seconds, in the results table
Repeat steps 1 - 6 using the different concentrations of sodium thiosulfate solution described in the table:
Repeat each experiment three times
Na2S2O3 + 2HCl → 2NaCl + S + SO2 + H2O
Solid sulfur is formed which precipitates in solution, turning cloudy:
Materials:
Stopwatch
White paper with cross marked on it
100 cm3 conical flask
100 cm3 measuring cylinder
10 cm3 measuring cylinder
2.0 mol/dm3 dilute hydrochloric acid, HCl (aq)
40 g/dm3 sodium thiosulfate solution, Na2S2O3 (aq)
Hypothesis:
A precipitate will be formed quicker if the concentration of the reactants is greater
Objective:
To investigate the effect of changing concentration on the rate of reaction by measuring the formation of a precipitate