Independent Variable: I will be changing the amount of mixture containing the three molar hydrochloric acid and water. This is to see how much the concentration of acid affects the speed of reaction to the marble chips. I will have 30 ml of mixture and split it in to three to get three results to gain an average. The concentrations will be in the ratios of 30 acid:0 water, 25 acid:5 water, 20 acid:10 water, 15 acid:15 water and finally 10 acid : 20 water. This is an appropriate range of results as there is not a huge gap between them. From these ranges, it will be easy to view trends and patterns and anomalous results.
Dependent Variable: I will be measuring the rate of reaction. I will measure the rate by timing how long it takes for the water in the measuring cylinder, to reach a certain point/mark on the cylinder. In this case I will time how long it takes for the water to reach the ’50 ml’ mark. If I keep the same stop point at ’50 ml’, I will be able to recognise the affects on the speed of reaction with the different concentrations.
Fair Test: I will keep the same overall amounts of mixture of hydrochloric acid and water in the conical flask. The amount of mixture will be 30 ml. I will use the same stop point which shall be at 50 ml. I will keep the same mass of marble chips, which will be 10g and the surface area of the marble chips. I will carefully wash out the equipment and apparatus to prevent contamination of the apparatus and keep the temperature in which I will be experimenting in at room temperature, around 25 degrees Celsius.
Apparatus: Conical Flasks.
Measuring cylinders.
A large bowl.
*Bee hive.*
Tap water.
Bung with tube.
Marble chips.
Electronic weighing scales.
Stop clock.
Safety goggles.
Hydrochloric acid.
Diagram:
Safety: To keep safe…
Tuck in stool, ties and tie back hair and ensure a clear working space.
Clear up any spillages of acid. Acid is a highly corrosive chemical and is very strong when it is 3 molar hydrochloric acid.
Step Plan:
- Collect apparatus and set up as shown in diagram.
- In a measuring cylinder, pour in 30 ml of 3 molar hydrochloric acid and 0ml of water.
- Fill a measuring cylinder with water and don’t let any air or water out of it.
- Place it on top of the bee hive.
- Out of this 30 ml mixture pour 10ml of it in to the conical flask.
- Using the electronic weighing scales, measure 10g of marble chips.
- Add the 10g of marble chips.
- Then place the bung on top of the conical flask to stop gas escaping.
- Start the clock immediately!
- When the water in the measuring cylinder falls to the 50 ml mark, stop the clock.
- Record the time in a results table similar t the one below.
- now repeat the steps for 25ml HCl:5ml water
- Repeat for 20ml HCl:10ml water
- Repeat for 15ml HCl:15ml water
- And repeat for 10ml HCl:20ml water
- Repeat all the above steps twice more so by the end of this experiment you should have three results for all 5 measurements.
Results Table:
