Method
Firstly we will put on our safety glasses to prevent any damage to our eyes if any acid were to fizz up. Next we will gather up all our equipment, Next we will get a clamp stand and attach a clamp to it and then attach a gas syringe holder to the clamp, when will make sure that the gas syringe holder is clamped very tightly to the clamp to make sure that the gas syringe will be kept still and wont move whilst the experiment is in progression. Post doing this we will place our gas syringe in to its holder and make sure that the gas syringe is lying horizontal as to allow only the gas to push the middle of the syringe. Next we will place a delivery tube to the end of the gas syringe. Next fill a measuring cylinder with 20 cm³ of 2.0mol Hydrochloric acid and pour this into a conical flask and the place the conical flask just beside the bung of the delivery tube ready for the start of the experiment. In order to conduct the experiment we need marble chips, to start the experiment we weighed out 2 grams of small-sized marble chips, (we decide on 2 grams as we conducted some preliminary experiment and found that 2 grams were the easiest to use and gave us the widest range of results) and held in our hand. Next I then placed them in the conical flask of acid and then my partner as quickly as possible put the bung of the deliver tube into the conical flask. At every 10 second interval up to 50 s we checked the reading on the side of the gas syringe and recorded it. We then repeated the experiment a further two times for using small-sized marble chips so we had acquired 3 result. We repeated the experiment again a further 3 times when using medium-sized marble chip and another 3 times using large-sized marble chips. So we hds 3 sets of results for small-sized marble chips, 3 sets of results for medium-sized marble chips and 3 sets of results for large-sized marble chips.
Risk Assessments
There were very few risks when carrying out this experiment. We had to wear safety glasses at all times to prevent any chemicals from coming into contact with our eyes. We used 2.omol Hydrochloric acid which can be fairly harmful when in contact with skin so whenever I got some on my hands I was instructed to wash it off promptly to prevent any irritation
Equipment List
Conical Flask
Delivery Tube with bung
Clamp stand
Clamp
Small, medium and large sized Marble chips
2.0mol Hydrochloric acid
Measuring cylinder
Gas syringe
Gas syringe holder
Stop clock
Scales
Safety glasses
Diagram
Preliminary work
We conducted a number of preliminary experiments to decide on which variables to use, firstly:
1. 5g of small, medium, large marble chips, and 50 cm³ of hydrochloric acid.
Small
10s 39cm
20s 72cm
30s + 110 cm, middle of syringe had been pushed out unable to record any results
40s
50s
Medium
10s 24cm
20s 56cm
30s 88cm
40s +110cm middle of syringe had been pushed out unable to record any results
50s
From conducting these two experiments it is clear to see that the rate of reaction is clearly too fast as already over 100cm3 of gas has been produced before 50s has passed. We have to limit the two variables here.
2. 3g of small, medium, large marble chips, and 20 cm³ of hydrochloric acid.
Small
10s 24cm
20s 57cm
30s 87cm
40s 103cm
50s 110cm+
Medium
10s 25cm
20s 44cm
30s 65cm
40s 78cm
50s 92cm
Large
10s 22cm
20s 40cm
30s 58cm
40s 70cm
50s 83cm
From conducting these tests it can be clear to see that these variables allow a wider variety of results but with the small marble chips more than 110 cm was produced before 50s was up so 1 of the variables needs to be lowered.
3. 2g of small, medium, large marble chips, and 20 cm³ of hydrochloric acid.
Small
10s 17cm
20s 42cm
30s 65cm
40s 85cm
50s 105cm
Medium
10s 12cm
20s 27cm
30s 43cm
40s 60cm
50s 76cm
Large
10s 8cm
20s 17cm
30s 37cm
40s 47cm
50s 58cm
These results show that I will be able to conduct the experiment to obtain the best possible results.
I will therefore use
2g of small, medium and large marble chips,
20 cm³ of 2.0mol Hydrochloric acid.
Obtaining
Variables
2g of small marble chips
2g of Medium marble chips
2g of Large marble chips
20cm³ of 2.0mol Hydrochloric acid
A table to show how much gas is give off from marble chips being reacted with Hydrochloric acid
Results Table
I am now going to ad a table of all the average of the three readings
We can see that the amount of gas given off after 50 seconds ranged from 38cm³ to 105cm³. 50s seemed a good point to stop as the highest reading was 105 if we had gone up to 60s for example we wouldn’t have been able to take down a reading.
Analysis
From using our graph we can work out the amount of gas given off per second, (using our average reading) by working out the gradient.
Y/x –rate of reaction,
Volume of gas given off
Time
Small sized marble chips
90-0 = 90
90/50 = 1.8cm/second
Medium sized marble chips
69.93-0 = 69.93
69.93/50 = 1.3986 cm/second
Large sized marble chips
42.33-0 = 42.33
42.33/50 = 0.8466 cm/second
Conclusion
It is clear to see that the 2g of small sized marble chips has the greatest rate of reaction this is over double the rate of reaction for 2g of large-sized marble chips proving that increasing the surface area of a the chips will increase the rate of reaction.
The 2g large chips had roughly half the rate of reaction than that of the 2g of the small ones so I can conclude that by having double the number of chips to react with the reaction rate is doubled as well.
Evaluating
Accuracy
Accuracy of results was key factor in our experiment, a reason for this may be down to human error, for example there were a few key seconds between placing the marble chips into the acid and putting the bung of the delivery tube into the conical flask, in these few second the reaction would have started and gas may have been given off but not have been able to have been recorded. Another factor was when weighing out the marble chips, it was often very difficult to weigh out exactly 2 grams and often the nearest possible weight would have had to be taken (e.g. 2.07g). The Gas syringe only had a capacity of 110 cm thus only allowing us to conduct the experiment for a limited time and not allowing us to make any further observations of the results,
e.g. whether or not the same amount of gas was produced each time regardless of surface area.
My prediction regarding doubling the surface area doubles the rate of reaction is in conclusive as there is no way of defining the surface area of the marble chips, they were just either small, medium or large, and in many cases the marble chips within the small group differed in size as with the medium and large groups.
Improvements
Several improvements I can make to my experiment are, using a large gas syringe to allow more time and to gain a wider span of results. Having the facility of finding out how to define the surface area of marble chips to be able make more accurate conclusions and be able to find out more observations in results. We could’ve recorded the amount of gas being produced every 5 seconds as opposed to 10 to have gained more results and therefore more accuracy.
Another experiment we may carry out could by how varying the concentration of hydrochloric acid we use as will affect the rate of reaction with marble chips. If we varied the concentration of acid as well as the surface area of the marble chips we would gain a lot more results and may be able to make further conclusions.
E.g. would the amount of gas given off stay the same if the surface area wereb changed?
