Rate experiments involving precipitation (Edexcel GCSE Chemistry Combined Science): Revision Notes
📚 Revision Notes
Rate experiments involving precipitation
Reaction between Sodium Thiosulfate and Hydrochloric Acid
When sodium thiosulfate reacts with hydrochloric acid (HCl), a yellow solid called sulphur forms. This makes the solution go cloudy. We can use this cloudiness to measure how fast the reaction happens by timing how long it takes for the solid to form.
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Steps to Carry Out the Experiment
- Measure the Solutions:
- Use a measuring cylinder to measure out fixed amounts of sodium thiosulfate and hydrochloric acid.
- Heat the Solutions:
- Warm both liquids to the temperature you want using a water bath.
- Mix and Time the Reaction:
- Pour the two solutions into a conical flask. Place the flask over a piece of paper with a black mark (like a cross) on it.
- Start the timer as soon as you mix the solutions and stop it when you can't see the black mark anymore through the cloudy solution.
Variables to Keep the Same
- Temperature: You can repeat the experiment at different temperatures to see how it affects the reaction speed.
- Volume: Make sure you always use the same amounts of sodium thiosulfate and hydrochloric acid.
- Concentration: The concentration of both solutions must stay the same throughout the experiment.
How Temperature Affects the Reaction
- Higher Temperature: The higher the temperature, the faster the particles move. This makes them collide more often, so the reaction happens quicker.
- Shorter Time = Faster Reaction: If the black mark disappears quicker, the reaction is happening faster!