Thiosulphate (doesn’t matter what the formula is but thio as a prefix indicates a sulphur compound) ions react with the hydrogen ions in acids to produce a thick precipitate of sulphur. The reaction happens faster at higher temperatures.
We can compare speeds of sprinters by measuring how long it takes for them to run a fixed distance, 100m. The world record held by Usain Bolt is quoted as a time, 9.58 seconds. The smaller the time taken to cover 100 meters the faster the speed.
We can time how quickly enough sulphur is produced by the thiosulphate ions to completely block a black band on the back of a test tube.The equation for this reaction can be written as:
Thiosulphate ions + hydrogen ions —–> sulphur + other products
Homework:
Watch the video. Decide how long it takes for each reaction in the video to produce enough sulphur to hide the black mark.Draw up a table of results. Plot a graph of temperature against time taken for the reaction( temperature goes on the horizontal axis, this is the variable you have control over.
Do an experimental write under the headings (on loose paper)
Aim
equipment
Diagram
Method
table of results
graph
Conclusion. What happens to the rate of reaction as the temperature increases?
Discussion: Use particle theory to explain the effect of heat on the rate of reaction with thiosulphate and hydrogen ions. Words to use in the discussion include activation energy, kinetic energy, effective collisions, frequency of collisions.
Play the presentation Chemical equations and calculations. Pay particular attention to the worked example before doing the example at the end of this post
Example to be handed in tomorrow
Hydrochloric acid solution was titrated with standard sodium hydroxide solution.
Before the titration the acid was diluted by making 1ml of solution up to 20ml(1:20) in a volumetric flask
20 ml samples of the acid in conical flasks were titrated by running standard sodium hydroxide solution ( 0.15 molL-1 concentration) in from a burette using phenolphthalein indicator
Titration Results
Volume of hydrochloric acid=20ml
Titration
rough
titration 1
titration 2
titration 4
titration 5
Final volume (ml)
26.35
49.60
24.50
50.00
47.80
Initial volume (ml)
00.00
25.20
00.20
27.00
23.30
Titre (ml)
26.35
24.40
24.30
23.00
23.50
On your own paper:
write the heading Titration Calculation
Copy the table of results beneath
select three concordant results and calculate the average titre
Write down the balanced chemical equation for the reaction
Use the method you have been shown to calculate the concentration of the hydrochloric acid
