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Chemistry coursework Aim: To investigate the rates of reaction for Calcium Carbonate (CaCO3) and Hydrochloric Acid (HCL). Hypothesis: I think that the higher the concentration of acid, the quicker the rate of reaction. This is because the higher the concentration of acid the more particles there will be in a given space. If there are more particles in a given space, then there will be more frequent collisions. The more frequent the collisions are, the higher the probability will be of any collision having enough energy to react. This is in accordance with the collision theory, which states that “ for a reaction to occur particles must collide with enough energy and in the right orientation, in order to facilitate a reaction”. The minimum amount of energy required is called “activation energy”. Planning: In this experiment I will be investigating the reaction between CaCO3 and HCL. I will add these products together and investigate how different variables affect the rate of reaction. I will observe and monitor the reaction, whilst collecting results. I will interpret these results onto a graph to help me look for a trend between the rate of reaction and my chosen variable, which I will monitor and change. I will then attempt to explain these results through scientific reasoning. I will also look for any anomalous results and further identify, discard and repeat them. I have decided a hypothesis based on scientific reasoning including the collision theory and activation energy, and I will refer to this in the conclusion. I will compare this to my discoveries and finally evaluate my whole investigation. The variable that I will be measuring is the concentration of acid in cm3, for the concentration of acid I will use 0.5 molar, 1molar, 2 molar and 3 molar. This will be our variable that we will change. I chose concentration of acid to be my variable that I will change for specific reasons. One reason is my background scientific knowledge of how concentration affects rate of reaction. This adds “interest and purpose” to my experiment, and means that I can interpret my results scientifically. Another reason is how easy it is to control. Concentration of acid in an experiment is easier to control because it involves minimum error and does not change. To look for how concentration effects the rate of reaction, I will need to keep all the other variables as constant as possible within my reach in this classroom environment. All of these further variables I will control then; Volume of acid, mass of CaCO3, temperature of the area we are doing the experiment in, pressure of the surroundings, type of acid, the surface area of CaCO3 and the equipment used. For the volume of acid we will measure out 50 cm3, this will have a small inaccuracy due to meniscus, and this is the slight dip in the middle of the liquid because it slightly sticks to the sides. I will measure the mass of CaCO3 at a constant of 5g, although there will be a small inaccuracy due to the balance of the scales showing it to one unit behind the decimal point this means we would not know if the mass was 0.05g or 0.09g. I will be doing the experiment under room temperature, and the air pressure will be whatever the classroom environment is, but this will not vary enough to change the experiments outcome. The type of acid will be hydrochloric acid (HCL) and the Calcium Carbonates (CaCO3) surface area will be maintained as marble chippings throughout the experiment. I will also keep the equipment used the same and I will clean the equipment after each test to make sure that the conditions are exactly the same at the start of each experiment. These other possible variables involve possible error when conducting the experiment, which if risked, would decrease the accuracy of the results. For example, volume of acid would be hard to measure when looking in to the measuring cylinder because the “reading lines” are not perfectly clear for a human to read and the “meniscus” (concaved shape formed at the surface of the water due to the sticking of particles to the sides of the container) also produces a deceiving reading to humans. Temperature could be changed but it would be difficult to do within a classroom environment. The Type of acid is another variable, which cannot be used because we don’t have enough at our disposal. However, human error will be involved in almost all variables of my experiment therefore, it is difficult to control or keep the same. In my evaluation I will further comment on the faults of my experiment. The way in which I have decided to investigate the relationship between concentration and rate of reaction is as follows. I know that gas will be produced in the reaction. I also know that the speed of production of this gas is governed by the rate of reaction. Therefore I feel that the rate of gas production will if monitored accurately, effectively represent the rate of reaction for each concentration of acid. Initially, my preliminary test for this was highly inaccurate.
Approximate Word count = 3431
Approximate Pages = 13.7
(250 words per page double spaced)
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