Rates of Reaction Coursework

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Rates of Reaction Coursework Robert Flack 2002

0072 class 11KN

Aim

The aim of this investigation is to find out the factors which affect the rates of reaction between magnesium and hydrochloric acid.

Equation: Mg(s) + 2HCl(aq) --> MgCl²(aq) + H²(g)

Magnesium will react with hydrochloric acid, because it is higher in the reactivity series that hydrogen. When the two chemicals react a displacement reaction will take place and the magnesium will displace the hydrogen in the hydrochloric acid forming magnesium chloride and hydrogen gas.

Prediction

Given the collision theory, I predict that the higher concentration of hydrochloric acid, the faster the reaction. This is due to the fact that there are more molecules in the acid likely to collide with the magnesium. The rate of reaction also relates to the surface area of the magnesium, the bigger the area the greater chance of collision and thus the faster the reaction takes place.

I also predict that the rate of reaction will be affected by the temperature, the higher the temperature the faster the reaction. Application of heat leads to molecules travelling at a faster speed (greater kinetic energy) and therefore more chance of collision with each other. Activation energy (Eª) will lead to the increased potential energy of molecules making a bigger reaction likely.

I expect the reaction to halve in time from 1M to 2M as there are double the amount of molecules in 2M than 1M.

Equipment

Test tube rack, test tubes, stopwatch, water, measuring cylinders, 4M hydrochloric acid, magnesium. Goggles should be worn for safety.

Method

There are several ways I could record the time of the reaction. I could use a gas syringe to collect gas evolved from the reaction and record the rate that way. I could weigh the test tubes before the experiment and cross section that weight with the weight of them after the reaction has taken place (giving the amount of hydrogen used). I could also time the reaction, which is what I am going to do

-Arrange the apparatus as pictured on the previous sheet.

-Measure out the 4M acid with the needed amount of water to form 9 different solutions each of different concentrations. They should be, 4.0M, 3.5M, 3.0M, 2.5M, 2.0M, 1.5M, 1.0M, 0.5M and 0.0M. This should be carried out using the measuring cylinders.
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-Pour each of the concentrations in turn into a test tube with equal amounts of magnesium every time present.

-Record the reaction time for each concentration (from pouring of acid into test tube to time when magnesium is no longer present)

-For fairness repeat experiment twice for each concentration

Preliminary Experiment

I will first carry out a preliminary experiment to know what to expect for the real thing and be able to make a more accurate prediction.

I used a smaller range of concentrations for the preliminary experiment. Including 1M, 1.5M, 2M and ...

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