Results
Below is a table showing the results for this preliminary experiment.
From the results you can see that the higher the concentration level of water the longer it takes for the cross to disappear. I have drawn a graph on the next page to show these results.
Graph
This shows that the higher the volume or concentration of thiosulphate the quicker it takes for the cross to disappear.
I shall now explain my next task. This will be my final experiment for this coursework.
Aim
To investigate the effect of temperature on the rate of reaction between magnesium and hydrochloric acid. There are four factors which affect the rate of reaction: concentration, catalysts, surface area and temperature. I have chosen temperature and concentration.
Background Knowledge
In my case the reactants are hydrochloric acid and magnesium ribbon. The chemical reaction takes place when the magnesium ribbon is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula for this experiment is:
Magnesium + hydrochloric magnesium + hydrogen gas
Metal acid
The reactants are: mg + 2hcl
As the concentration of acid increases the rate of reaction becomes faster because there are more particles. As they are more likely to collide and react with each other. As 0.5 mol has fewer chances of the particles colliding because, a more content rated acid has more amount volume of water. In more concentration of acid there will be fewer chances of the acid particles bouncing off, as there is more actuation energy and more chance of them colliding are reacting.
The picture shows a chemical reaction-taking place. In a chemical reaction the reactants collide with each other.
This picture shows low pressure.
This Picture shows High Pressure
The reason I predicted the higher the concentration the quicker the reaction will occur is because, there are more particles and there will be more collisions. There could not be a reaction if the substances couldn’t collide. “The more collision between particles in a given time the faster the reaction.’ This shows if we use 10ml solution of acid it will be less concentration and less particles, the slower the reaction. But where as if we use more acid 20ml solution of acid there will be more concentration more particles the quicker the reaction. “As we increase the concentration, the rate of reaction increases”. This is for 10ml of acid. For 20ml of acid there will be a higher concentration. More particles, more collision, faster the reaction. The more collision there will be the more altercation energy and the rate of reaction will occur quicker.
The concentration of the acid affects the rate of reaction because, the higher the concentration of the acid (let’s say 2 molars) will cause the reaction to happen quicker compared to a less concentrated acid (let’s say 1 molar). If the solution is made more concentrated it means there are more reactants colliding between the water molecules, which make the collision between the important particles more likely. In a gas, the pressure simply squashes the molecules together so there are more collisions. On the diagram below, on the left hand side there are less concentration, less particles and slower reaction. However on the right hand side diagram there is more concentration, more particles and quicker reaction occur.
For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.
Concentration – If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other.
Pressure – If the pressure is increased the particles in a gas are pushed closer. This increases the concentration and thus the rate of reaction.
Surface Area – If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of un-powdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas.
The particles in a gas undergo random collisions in which energy is transferred between the colliding particles. As a result there will be particles with differing energies.
Hypothesis (Prediction)
I predict that as the temperature is increased the rate of reaction will also increase. This means that the graphs which I shall draw should have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the temperature is increased. This can be justified by relating to the collision theory. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy.
Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur.
All this can be understood better with full understanding of the collision theory itself:
For a reaction to occur particles have to collide with each other. Only a small percentage results in a reaction. This is due to the energy barrier which has to be overcome. Only particles with enough energy to overcome the barrier will react after colliding.
The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area. Below is a rough example of the activation energy graph.
Apparatus
- Beakers – to pour each substance into
- Measuring cylinders – to measure the amount of each substance
- Stop clock – to time the reaction
- Conical Flask – to pour in all the substances and mix together
- Paper with a red cross – to watch as reaction takes place
- Hydrochloric acid – for the reaction to occur
- Water – for the reaction to occur
- Magnesium – for the reaction to occur
- Pipette – to take a small amount of solution
- Bunsen Burner – to heat solution
- Wire Gauze – to place chronicle flask on top of
- Heatproof Mat – to place Bunsen Burner
- Thermometer – to measure the temperature of the solution
Safety
A pair of safety goggles must be worn at all times and tongs should be used when handling hot beakers, test tubes and so on. A gauze and heatproof mat will be used to ensure that nothing catches fire or is burnt.
Fair Testing
In order for my results to be accurate my results must be achieved by carrying out a fair test. I will measure the amount of hydrochloric acid carefully and accurately. This ensures that there is no slowing down or speeding up of the reaction time. I will also carry out the whole experiment a second time to ensure that it was a fair and accurate test.
Diagram
Method
Firstly I will set up the apparatus as shown in the previous diagram. Then we are going to get some Hydrochloric Acid of different molar sizes. We have five different molar sizes: 0.1M, 0.5M, 1M, 1.5M and 2M. We are then going to mix each one of these different molars sizes of magnesium ribbons to see the ‘rates of reactions’. We will then measure each solution using a measuring cylinder. Then place a piece of plastic on top of the measuring cylinder, preventing water to spill out. Place a boiling tube on a test -tube rank. The boiling tube must have the magnesium ribbon placed inside it. Then we will pour the Hydrochloric Acid into the test-tube. When pouring the hydrochloric acid into the test tube I will make sure that I wear safety goggles. Start the stopwatch, and take the measurements of the reaction time, until it finally finishes. Then record the results into a table and then find out how to work out the average. I will repeat each experiment to make it a fair test.
Results
Below is a table in which I will place all of my gathered results at the end of the experiment.
I will then be able to analyse the results and see whether my hypothesis was correct or not. If it isn’t then I shall investigate further to see where I could have possibly gone wrong.
