Acid + Carbonate → Salt + Water + Carbon Dioxide
Hydrochloric Acid + Calcium Carbonate →
Calcium Chloride + Water + Carbon Dioxide
Hypothesis-
The more concentrated the acid the quicker the reaction will take place because there will be more hydrochloric acid particles than water particles for the marble chips to collide and react with. This means that more collisions will happen and there will be a quicker reaction time.
A larger surface area will also cause a reaction to happen faster. If the marble chips are powdered then the reaction will happen faster because more of the chip will be exposed to the acid and they will react quickly.
Increase concentration of acid → Increase reaction rate
Introduction-
Collision theory - Collisions between reactant particles are needed for the reaction to take place in order to form a product. Some collisions are successful and give a product while others don't because particles don't have enough energy.
Activation energy - The amount of energy needed for the reaction to be started. If there is enough energy then the reaction takes place and a product is formed, but if there isn't enough then no reaction takes place.
Diagram-
Apparatus-
A 25ml measuring cylinder
A 50ml measuring cylinder
Trough
Marble Chips
Acid
Water
Conical Flask
Delivery tube
Stopwatch
Method-
·Set up the apparatus as shown in the diagram
·Measure 50ml of acid into a measuring cylinder
·Put 2.5g of marble chips into the conical flask
·Measure 25 to 50ml of water into the measuring cylinder at the end of the delivery tube
·Put it into the water over the end of the delivery tube with your thumb covering the top of the measuring cylinder so that no water escapes and let go
·Pour the acid into the conical flask, place the rubber bung on the top of the conical flask and start the stopwatch
·Wait for the water in the measuring cylinder has gone then stop the stopwatch
·Record your results in a table
·Now try the experiment again but changing the concentration each time
Pilot Results-
Concentration ratio of acid to waterSize of Marble ChipsWater in measuring cylinder (ml)Time (s)
50:0Small5028.7
40:10Small2514.22
25:25Small2549.35
10:40Small25187.00
10:40Small25172.00
50:0Large2543.34
From my pilot experiments I found that using small marble chips was better than using large marble chips because the reactions happened faster. This is because the reaction has a larger surface area to act upon and so it will happen faster. I also decided that waiting for 50ml of water to be displaced from the measuring cylinder made the experiment last too long, so I am going to put 25ml of water in the measuring cylinder.
Final Experiment Results-
Concentration ratio of acid to waterSize of Marble ChipsWater in measuring cylinder (ml)Time (s)Average Time (s)
Ex.1Ex.2Ex.3
50:0Small2515.411.61313.3
40:10Small2519.422.718.620.2
30:20Small2534.5313533.5
25:25Small255247.734.244.6
20:30Small255752.355.454.9
10:40Small25212.2151180.4181.2
Analysis-
My first graph plots time on the x axis against the amount of acid in the solution. It shows that as the volume of acid decreases the reaction takes more time to occur. I do not have any anomalous results.
My second graph has the same axis but the level of water not acid. As the volume of water increases the reaction time also increases.
There does not seem to be a directly proportionate pattern in the results but we can see that, as I predicted, as the solution gets less concentrated the time begins to grow. Therefore this means that the weaker the solution gets the slower it takes to react. There is a great difference between the last two results (20:30 and 10:40). This is because in the last experiment the acid is very diluted and so the reaction takes a long time.
My prediction and the theory of the experiment fit well with my results. They show that- the more concentrated the acid the quicker the reaction will take place because there will be more hydrochloric acid particles than water particles for the marble chips to collide and react with. This means that more collisions will happen and there will be a quicker reaction time.
Evaluation-
I had no anomalous results in this experiment. These results are quite accurate but could be improved. If the experiment was done five times and then the average is taken then results would be more accurate. Also I could have started off with the lowest concentration of acid so that I could practice getting the bung on the top of the conical flask quickly.
Conclusion-
Overall the results obtained were quite accurate and showed that an increase in the concentration of the acid means that the rate of the reaction increases and the time taken is decreased.
