What affects the rate of a reaction? The reaction I will be investigating is the reaction of marble chip (Calcium carbonate) with hydrochloric acid.

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Jonathan Stockdale                         Chemistry Coursework      

Aim: I am going to find out what factors affect the rates of reaction.

The reaction I will be investigating is the reaction of marble chip (Calcium carbonate) with hydrochloric acid.

Balanced Chemical Equation!

Calcium carbonate + hydrochloric acid     Calcium Chloride + Carbon Dioxide + Water

          CaCO3(s)       +     2HCl(aq)             CaCl2(aq)    +       CO2(g)   +  H2O(l)

Variables:

The speed of a reaction depends on how often and how hard the reacting particles collide with each other, the theory is that particles have to collide in order to react; also they have to collide with enough energy to make the reaction happen, this is called the activation energy. The individual factors that affect the rate of reaction are; Temperature, Catalyst, Surface area, and Concentration.

 Temperature work by, at the temperature is increased the particles all move quicker, this means there will be more collisions, because of the increase in speed the collisions are going to be of greater force making it more likely that there will be a reaction and a form of new products; well this is the theory.

 A catalyst works by giving the reacting particles a surface to stick to where they can bump into each other; this in theory should increase the number of collisions.

Surface area is an important factor in rate of reactions because if one reactants is a large solid then breaking it up into smaller pieces will increase its surface area, this means that the particles around it in the solution has more area to collide with therefore should be more useful collisions; in theory this should increase the rate of reaction.

In theory more concentration means more collisions, this is because if the solution is made more concentrated it means there are more particles of reactant colliding between the water molecules in the solution used to dilute the solution, this makes collisions between the important particles more likely, if the particles are more likely to collide, then they are more likely to react, hence an increase in concentration causes an increase in reaction rate.

In my experiment I chose to use concentration as my independent variable. The reason why I didn’t choose temperature was because; I didn’t have the facilities to control the temperature precise enough that it would be an accurate test. The reason why I didn’t choose catalyst was because; I wasn’t able to get my hands on a catalyst that would be suitable and it would cost too much for me to buy a catalyst. So this left me with surface area and concentration, the reason why I didn’t choose surface area was because; with the resources available that would be practical for my experiment I was only able to get 3 sizes of marble chip; small, medium, and large, this was unpractical as I would only be able to get 3 sets of results where as I could a larger number of sets of results from concentration.

Which is the Best Technique?

The speed of the reaction can be observed either by how quickly the reactants are used up or how quickly the products are forming. It’s usually a lot easier to measure products forming. There are three methods that the rate of reaction can be measured by:

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  1. Change in mass – Measuring the speed of a reaction that produces a gas can be carried out on a measuring scale/mass balance. As the gas is released the mass disappearing is easily measured on the balance; the quicker the reading on the balance decreases, the faster the reaction happens.

  1. Downward displacement of water – This simply refers to the collection of gas using water. In this instance carbon dioxide is collected when it is given out from the reaction over time and is collected by an upside-down measuring cylinder filled with water, submerged under ...

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This piece of coursework is fairly well written but lacks detail. It covers the majority of the factors necessary to access the higher marks. However all need to be discussed in more depth with direct reference to the scientific theory that supports each. Improvements have been suggested throughout.