Rate of Reaction Chemistry Coursework

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The effect of temperature on rate of reaction

Introduction

Our investigation in rate of reaction involved us performing an experiment which involved us chemically reacting hydrochloric acid and magnesium. Different reactants cause different speeds and chemical reactions can vary from a small reaction to a large reaction. Reactions occur when particles of reactants collide together and react. The chemical reaction that we will be performing is:

Magnesium+ Hydrochloric Acid→ Magnesium Chloride+ Hydrogen

Through this reaction I will be measuring the amount of hydrogen that is produced. I will have to choose certain apparatus and a certain method which I will test in preliminary and then perform in my method.

Preliminary Investigations

Variables

Temperature- The higher the temperature, the faster the rate of reaction. This happens because at higher temperatures the particles have more energy meaning that they collide more with each other because the particles are moving around quicker. If you imagine a box of balls, if the balls have more energy they are moving faster and are more likely to bump into each other than balls with less energy and are moving slower. We can measure temperature in our experiment by heating the hydrochloric acid at different temperatures and measuring how much hydrogen is produced. This is the variable I will be changing and is going to be the thing I will be testing. So this variable will be allowed to change however I must still make sure that I have it at the correct temperature.

Concentration- The higher the concentration, the faster the rate of reaction. This is because there are more particles in the same amount of space. This leads to more collisions and more reactions. I can use this by changing the amount of hydrochloric acid and measuring how much hydrogen is produced. This variable in my experiment must stay the same, if I want to achieve reliable results. It has to stay constant otherwise it would be unfair and the results wouldn’t be reliable. I will keep it constant by using the same amounts of reactants for each experiment. I will have to decide on the amount of hydrochloric acid I use and the amount of magnesium I will use and keep them the same for every experiment that I do. If I do this I would have this variable controlled.

Surface Area- Any reaction in a solid has to take place at the surface at the solid. If the solid splits in two the surface area will increase. When the surface area of the reactant increases there are more collisions leading to more reactions. I also have to keep this variable under control otherwise I will get an unreliable set of results. If I don’t the results would vary and would not be very good. I will control this by when I am using the magnesium strips I will only make one cut out so the surface area of the magnesium will also be the same. I will have to decide on the amount of magnesium that I am using but once I have done that I will make sure that when I measure it I only use one strip of the magnesium. Otherwise if I have two strips the surface area of the magnesium will increase leading to greater reaction rate.

Catalyst

Catalysts are substances that change the rate of reaction without being used up in the reaction. Catalyst are used in industries to speed up chemical reactions leading to more of the product been produced and them getting more money. They are also efficient for industries as they also use high temperatures so they can reduce the amount of pollution. You can find lots of different catalysts in different reactions e.g. platinum in car converters. Catalysts work by lowering the amount of energy needed for the reaction to take place.

Practical

When scientists carry out an experiment to try and find evidence to come up with a scientific evaluation they must find a method that is full proof and that involves doing preliminary investigations to try and see if anything in their method will not give them accurate results. So for this investigation we performed a preliminary investigation so we could understand the sort of equipment that we should be using and the sort of chemicals that we should be reacting and the amount we should be using.  

So after looking at the task that has been set I knew that I had to decide and the sort of chemicals I would be reacting and the method and equipment I would be using. I also needed to decide on which variable I will be testing and which I will be using to do my experiment. After looking at what we would be doing I initially decided to test how temperature effects rate of reaction by reacting hydrochloric acid and magnesium. I decided to heat the hydrochloric acid at five different temperatures which were between 20-60˚C. We also decided to use 10ml of hydrochloric acid, after our first experiment with the solution at 30˚C we realised that using 10ml would be too much and that it wouldn’t be any good in getting any results. This is because the hydrochloric acid and the magnesium were reacting too fast and we didn’t have time to get a good set of results as it had all reacted after 20 seconds.

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After we tried to do the same but instead of using 10ml we used 5ml of hydrochloric acid. We also decided to only use 0.2 grams of magnesium. At first we were getting a good set of results but then we couldn’t see a pattern in our results. Most of our results were all over the place and we couldn’t get any reliable results. After looking at our method and our results we realised that we had to change something to get a better set of results. We had a look at changing the calcium carbonate to magnesium and ...

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This is well written laboratory report. The evaluation and analysis are good. The main improvements would be the collection of more data and an improvement in the scientific theory discussed within the introduction. The report shows good structure and a sound scientific understanding.