The purpose of this coursework is to investigate the factors which affect the rate at which zinc reacts with sulphuric acid to form zinc salt and hydrogen. There are a number of factors which affect rates of reaction and for my experiment I investigated the ways in which varying the concentration of sulphuric acid affected the rate of reaction between zinc and the acid. When planning for the experiments, I first tried to understand the theory behind a chemical reaction and the factors affecting rates of reaction. This is explained in Section 2.
Based on my understanding of the theory I selected one factor, concentration and made some predictions in Section 3 about how concentration levels affect the rate of reaction. In Section 4, I describe my methods and fair tests together with a list of the apparatus I used. To help in preparing for the investigations I carried out preliminary tests, which are described in Section 5. The results of my investigations are shown in Section 6 and my analyses of these results are found in Section 7. My evaluation is shown in Section 8.
Section 2 background information and theory When zinc is mixed with sulphuric acid, a chemical reaction takes place resulting in the production of zinc sulphate and hydrogen gas. The reaction is shown by the equation below: Zn(s) + H2SO4(aq) ZnSO 4 (aq) + H2 Collision theory The rate of reaction can be explained by collision theory. For a reaction to take place two things need to happen, a. ) collisions between particles must take place and b. ) the collision must have sufficient energy. Molecules are usually moving at different speeds and often bump into each other.
Often when they bump they don’t react but just bounce off each other because: They aren’t moving fast enough for the reaction to take place. However, occasionally they do hit each other so hard that reaction can occur and the rate of reaction depends on how often these mega bumps happen. Evidently the more mega bumps in a given time the faster the reaction. The most powerful collision is a fast, head to head collision as opposed to a slow glancing collision. It is not enough for molecules to collide. Bonds between the atoms must be broken before new molecules can be made.
This process requires energy. For every chemical reaction, there is a certain minimum energy needed in the collisions before a reaction can occur. This minimum energy is called the activation energy of the reaction. The higher the activation energy the less chance there is for successful collisions. When the new bonds are made energy is released. From collision theory we know that for a reaction to take place the zinc and sulphuric acid molecules must collide with each other and furthermore those collisions must have enough energy to perform the reaction.
The more collisions there are the faster the reaction and the harder each collision the faster the reaction. The sulphuric acid particles are in constant motion and they collide with the static zinc atoms. The factors that affect the rate of reaction between zinc and sulphuric acid a. ) concentration of acid A higher concentration of acid will result in a faster rate of reaction because there are more sulphuric acid particles which leads to a greater chance of them reacting with the zinc.
With a lower concentration the particles of sulphuric acid are more spaced out with more water present which reduces the chance of them reacting with the zinc. b. ) surface area of reactant A greater surface area of zinc results in a faster rate of reaction, because there is a greater area for the particles of the acid to attack and therefore the chances of a successful collision are greater. The fastest reaction will therefore take place when the zinc is in fine powder form. c. ) presence of catalyst
The presence of a catalyst speeds up the reaction because a catalyst lowers the activation energy level required for the reaction to take place, the presence of a catalyst results in more successful collisions while the catalyst remains unchanged in form. d. )temperature A higher temperature results in a faster rate of reaction. In a reaction with a high temperature the particles of acid move faster which means they collide more often and have more energetic collisions thus the rate of reaction is faster. For any 10i?? C rise in temperature the rate doubles. e. ) pressure
A higher pressure results in a faster rate of reaction. This is because an increase in pressure ultimately results in an increase of concentration, resulting in a greater chance of successful collisions. This does not apply to my experiment as I am not considering any gas. For my investigation I decided to investigate the way in which different concentration levels of sulphuric acid affect the rate of reaction, and in the next section I will make some predictions. The reason I chose to investigate this topic for my coursework is because I have already studied and read about it as part of my G.
C. S. E syllabus and so I am knowledgeable and dextrous with all areas of the investigation. It is also a practical investigation and a topic which I find relatively interesting. Section 3 – prediction Prediction1: I also predict that as you increase the concentration of sulphuric acid the rate of reaction will also increase. Prediction2: I further predict that the rate of reaction will be proportional to the concentration of acid. For any given quantity and surface area of zinc, doubling the concentration level of sulphuric acid will double the rate of reaction.