Concentration: this is the factor I'm going to study I will use the concentrations 0mol, 0.5mol, 1mol, 1.5mol and 2mol.
Temperature: This has big effects on the rate of reaction because the hotter the reactants are the faster they react, this is because the molecules of the reactants move around more and faster so collide more often and quicker, as they collide they react, therefore as according to the collision theory the reaction is sped up.
Catalysts: catalysts lower the activation energy of a reaction so with less energy needed to start the reaction the energy can go to making the reaction quicker.
Method:
In this experiment first we will make up the concentrations of the 0.5mol, 1mol and 1.5mol acids by diluting the 2mol with distilled water at the Ratios 1:3, 1:1 and 3:1, for the 0mol we are using distilled water. After making up the concentrations of acid we will mix 25ml of Hydrochloric Acid with 25ml of Sodium thiosulphate in a beaker. We will measure the quantities for the concentrations and for the reactants with a measuring cylinder that can measure to the nearest milliliter for good accuracy. We will pour the reactants into the beaker using a funnel in order not to spill any because if we do it will mean we wont have a fair test and we will have acid and harmful chemicals on the table which will be dangerous. We will place this beaker over a cross on a piece of paper, we will look through the beaker at the cross and measure the time it takes for the liquid to go cloudy enough so we can't see the cross. We measure the time using stopwatches. We will do this 3 times each for the concentrations of 0mol, 0.5mol, 1mol, 1.5mol and 2mol. We will then collect the results into a results table and draw a graph.
Results table:
Analysis:
In my experiment I used a concentration of 0 and from my results you can see that I didn’t get any results for this because if the concentration is very low or 0 then its going to take an infinite amount of time to react if the concentration is very high then its going to react very quickly but it will always take an finite time no matter what the concentration is.
My graph of the averages of all 5 concentrations has an anomalous result that shows that somewhere with the 1.5 mole the experiment went wrong e.g. accidentally got the wrong solutions or miss timed the experiment. Although 1.5 moles had gone wrong in both experiment 1 and 2 so it may be due to a flaw in the method itself. My graph goes in a curve downwards because the 0.5moles takes a longer time than the others and when it’s the 1 mole it takes quite a bit less time than 0.5 moles, 1.5 then goes up causing it to be the anomalous result and 2 moles isn’t much different to 1 mole and 1.5 mole the difference between them is averagely 2 seconds.
My prediction was correct because I said that when you increase the moles of an acid the reaction rate will be quicker than that of 0 (distilled water) moles. So the collisions between the reactants got more and more and faster and faster.
Evaluation:
The experiment we did I thought was very accurate, or at least as accurate as we could get it. If we could do it again I would perhaps not use 0 moles (distilled water) as it takes an infinite time to react with the Sodium thiosulphate, or change a different variable like temperature of the acid or Sodium thiosulphate. The results are also reliable because they do show the amount of time decreasing when the moles of acid increase, even though there is a anomalous result, 1 out of the 3 tests done was correct so there was a third of a chance it coming out correct making it into the curved line of best fit. I think our method was good and was probably not the cause of the anomalous result, but may be somewhere extra sodium thiosulphate was added by accident. To make the test fairer I could also try to keep the temperature constant. Also whoever timed the experiment could have gone a few seconds out causing the reaction to last longer than it should have. I think that my evidence is sufficient enough to support my results and I feel that my method worked well. To improve the accuracy of the timings I would consider using a light sensor hooked up to a computer, which automatically stops the stopwatch when light intensity decreases after a certain point, in other words when the solution becomes too cloudy it stops the stop watch which means each test is stopped at the same point therefore the accuracy of each test is improved.
