• Sulphuric Acid
• Nitric Acid
• Hydrochloric Acid
What I will need:
• A plastic container such as a butter tub
• A timer
• A bung
• A small boiling tube
• A larger boiling tube
• Water
• Hydrochloric Acid
• Measuring tubes
• Marble chips
To test the acids, we filled the butter tub with water, then the larger boiling tube as well and carefully manoeuvred it so that it was upside down in the butter tub of water with no air in. We then measured out the right concentrations of acid to water (1:10). We measured out exactly 5 grams of marble chips and put them in the smaller boiling tube. As someone stood by the timer, ready to start it, someone else added the mixture of acid and water together in the smaller boiling tube with the marble chips in. Quickly, we covered the top of the boiling tube with the bung and started the timer. After 5 minutes we looked at the experiment to see how much air had gone up into the larger boiling tube. We were careful not to spill any acid or break any of the equipment whilst doing this experiment. To make the experiment a fair test, we made sure that every 5 grams of marble chips was exactly 5.00 to two decimal places. The experiment looked like below. We also made sure that the room temperature was exactly the same every time before the experiments.
As Hydrochloric was the only acid to react at all, we decided to use it. Even though only 4ml of air was collected, the concentration of the liquid we added was very weak, therefore a big reaction could not have taken place. I concluded that Hydrochloric acid is a reactor. We were using the lowest concentration of acid so that we could see the slowest reaction rate.
Now that I had completed my preliminary experiments, I decided on my final one. I will repeat the experiment as above, except this time instead of varying the acid type, I will change the concentrations. Each time I do the experiment I will have 10ml of liquid. I will start off with the ratio of water to acid 10-0ml, then carry on to do 9-1ml, 8-2ml, 7-3ml, etc until I get to 10-0ml. To make it a fair test, I will use exactly 5.00g of marble chips, size 6-9mm each time. I won't change to the powder marble or any other size. I will conduct each experiment fairly and not change anything.
To get detailed, precise results, I will conduct the experiment three times. This will ensure accurate data.
I predict that the higher the concentration on acid, the quicker the reaction will take place as Hydrochloric acid is a reactor. Reaction rates can be increased if the concentration of reactants is increased. An increase in concentrations produces more collisions. The chances of an effective collision goes up with the increase in concentration. I also think that when the ratio of water to acid is 10-0ml no reaction will take place because water is a neutral liquid. I think that the reaction time will change equally each time a higher ratio of acid is added.
After carrying out the experiments, then repeating it three times I collected and recorded the information on graphs which I have printed out. Unfortunately, sometimes after waiting for 5 minutes, there was still hardly any reaction at all. I did not show these results on the graph as there was hardly anything to show. I have written the information I gathered below.
From looking at my graphs I can establish a few things. As the concentration of acid got higher, the reaction time massively decreased. At the beginning hardly any air was coming out, but by the end it was getting to 30ml in less than 30 seconds. My prediction that the time would get less every time more acid was added was correct, although I thought that the decrease would be steady and it wasn't. Usually from either 40% or 50% the reaction would suddenly increase dramatically. It would go from hardly any reaction in 5 minutes, to getting to 30ml in under two minutes.
My graph sheet shows all three of the tables of information. I was confused by how long it took for the third chemical reaction to get started. It seems that, that line starts off a lot higher than the other two. Even though they all start off at completely different places, the final results were all within a second of each other.
I think I can safely say that the data I used was fairly reliable. This is because I repeated the experiment three times so the evidence I found would be pretty solid. The only anomalous results were on the 50% to 60% on the line graph, the line actually goes up instead of decreasing like all of the others had. I am unaware of what caused this.
If I were to do the experiment again, I would definitely find a way to include all of the results. By the time I realised that I would not be able to include all of my results on one graph it was too late and I couldn't go back and do the experiments again. Next time I would not wait until each passed 30ml, or 5 minutes went past, I would perhaps just see how far each went after 5 minutes. That was I would be able to include all of my data onto one graph. I would repeat the experiment again three times though as I think this helped me a lot in seeing what numbers were anomalous or abnormal in the chart. To take this investigation further, I would suggest doing it again more than three times, or testing more types of acid, or using different sizes of marble chips.
Next time I could also try experimenting with different factors which affect the rate of chemical reactions. I could add a catalyst to acid and marble chips using the same principles as the last procedure. Or I could see what happened if I heated the acid, water and marble chips and record how quickly air collected in the boiling tube. The colliding molecules would provide a quicker reaction. I could start off with a more concentrated acid next time, or maybe use more exact measurements. I could have concentrations to 1.5, 1.6, 1.7 etc.
