Sodium thiosulphate is a colourless, crystal like compound and is used for dyes and is also a salt. Hydrochloric acid is colourless, poisonous and highly acidic. It is often used as a chemical intermediate and in petroleum production, food processing, pickling, and metal cleaning.
It can also be found in the stomach. These chemicals are perfect for my investigation because they are both clear and colourless. This is good because I will instantly be able to see any change in the solution. The state symbol for sulphur dioxide is aq not g because it is dissolved in water as its original state would be too toxic and corrosive for me to use safely. I am investigating the different factors which may speed up chemical reactions. Rates of reaction vary depending on which chemicals are being used and the activation energy required. Reactions that occur slowly have a low rate of reaction.
Reactions that happen quickly have a high rate of reaction. For example, rusting is a slow reaction; it has a low rate of reaction. Burning and explosions are very fast reactions: they have a high rate of reaction. Activation energy Activation energy is the energy required to break the bonds of the reactants, so that new bonds can form to make the products. An input of heat energy is required to start some reactions.
This energy gives the reactant particles enough energy to collide with enough force to break apart the bonds so that new products can be made from atoms. The enthalpy change is the amount of heat absorbed or released when a chemical reaction occurs at a constant pressure. I decided that it would be best for me to use a bold marker pen to make the mark more visible under the conical flask. This ensures that the solution is completely opaque when I stop the timer. The conical flask and all other equipment must be clean as any impurities may contaminate my experiment.
A grade GCSE chemistry coursework - Rates of reaction Decomposition of sodium thiosulphate
Also, it has a narrow top and so it is safer. Using white paper helped the marking to stand out. I used this to gauge when to stop the reaction — when the black x was obscured by the white sulphur precipitate, the timer was stopped. I tied my hair back, tucked in my tie and pushed all stools and bags under the desk where there is no risk of anyone tripping.
I had to make sure that my classmates were safe as well as myself. I made sure that I had everything before I started. This makes sure that my experiment runs smoothly. I also made sure that the measuring cylinder was on a level surface so that I could clearly see how much liquid I was putting in to it. As soon as the chemicals were in, I started the timer. I did not swirl these together because I wanted to see the rate of reaction without any intervention. The timer was stopped when in see the black cross through the cloudy solution could no longer. I wrote down my results and then moved on to the next concentration of sodium thiosulphate.
This is very important because loose hair can not only get dipped into chemicals but can also obscure vision. I also made sure that any clothing or long jewellery was clear and out of our way as clothing can also get caught. I tucked in my tie and shirt, and took off my blazer. I stood up to allow more space for others to walk by between the rooms. Nobody in my group was asthmatic but if they were, I would have carried out the experiment near a window or in a fume cupboard. Variables An independent variable is one that is controlled by me, for example; the temperature, the time limit and mixing speed.
Dependent variables are not controlled by the experimenter. The independent variables in our experiment are the concentration of hydrochloric acid. The dependent variable was the rate of reaction. Use of rate of reaction in industry The chemical industry makes medicine and many other substances such as; Limestone - this is used for building Sulphuric acid — used to make other substances Ammonia - used to make fertilisers.
Conclusion In my investigation, my data and my graphs proved that my hypothesis was correct.
For example, when my concentration was 1M the average reaction time was seconds, and then when the concentration was 5M the average reaction time was seconds. I did have some outliers in my results; however I think that the experiment went fairly well overall. I have calculated the gradient of my line to support my hypothesis and found that: For every one M increase, the rate for reaction increases by 2.
I did, however find some outliers in my results. These are circled on my graphs. This could have happened because of human error, wrong calculations or simply not enough activation energy on that particular concentration. I will discuss these further in my evaluation.
Graphs All of the graphs that I drew for this investigation show a negative correlation. This shows that as you increase the independent variable the concentration , the other variable the time taken for the experiment , went down. This fits in with my hypothesis and my data. In my scatter graph with line of best fit, most of the points are close to the line. This shows that my data is quite accurate. There are a few mild outliers.
The results for 1, 2 and 4M keep showing outliers. This could have happened because of calculation errors, human errors, recording errors or a fault with the equipment that we used.
- Accessibility links;
- Chemistry Rate of Reaction Coursework for Calcium Carbonate and Hydrochloric Acid.
- GCSE Science/Rates of reaction coursework - Wikibooks, open books for an open world.
- GCSE Chemistry Coursework on Rates of Reaction - GCSE Science - Marked by momafimans.tk.
The points in the top right are quite far down so this shows a negative correlation. This good because it shows that for every increase in concentration is a decrease in rate of reaction. This is supportive of my conclusion. My Error bar graph shows a negative correlation.
The bars of 1M and 2M overlap and this shows that there is no real difference. It is important to remember that a rapid reaction is completed in a short period of time.
Chemistry rate of reaction coursework - GCSE Science - Marked by momafimans.tk
An example of a fast reaction is an explosion, and an example of a slow reaction is rusting. The 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. Therefore, the products of the reaction are magnesium chloride and hydrogen gas.
For my experiment the results will be measured with a stop clock and the length of time the magnesium takes to dissolve will be measured. The results will be taken down in a table, and then a graph will be drawn from the information. The concentration of hydrochloric acid is calculated by moles and I will vary the concentration from 0. Each time, a 1cm strip of standard width magnesium ribbon will be used.
Each time Rates of reaction between magnesium ribbons and hydrochloric acid. GCSE coursework..