To investigate the effect of temperature on the rate of a reaction

GCSE Science

Max Askwith. 11 Chemistry 1. Chemistry Coursework. 2002.

Investigation

Aim

The Reaction

Magnesium metal + hydrochloric acid ➔ Magnesium chloride + Hydrogen gas

Mg (s) + 2HCl(aq) ➔ MgCl2(aq) + H2(g)

Prediction

I have found for other experiments that the higher the temperature of a reaction the quicker the reaction takes place. Because of this I will predict that as the temperature rises, the rate of the reaction will rise as well.

Scientific Explanation

Increasing several factors can increase the rate of a reaction. You can increase the concentration, the surface area or the temperature of the acid or metal. The only factor being varied in this experiment is temperature. So the others must be constant.

The rate of any reaction depends on the frequency of collision of reacting particles with a minimum amount of energy for a reaction to occur. Having a higher temperature increases the energy of the collisions because it makes all the particles move faster. This means a greater proportion of the particles have enough energy to react when they collide. This will increase the rate of reaction. Also if the particles are moving quicker the time between collisions is less and more collisions will take place per unit time, meaning more reactions will take place, further increasing the rate of reaction.

Pilot Experiment

Aim:

To find out which combination of either magnesium powder or magnesium ribbon to use in conjunction with either hydrochloric acid concentration 0.5ml or concentration 1.0ml for our experiment on the effect on temperature when a reaction takes place, so we will need to find a combination of magnesium and hydrochloric acid which will produce a steady rate of reaction at room temperature and will still be measurable at 30ºc

Method:

Set up equipment as shown by diagram.
Take a 3cm strip of magnesium ribbon and clean it with some glass paper.
Pour 50cm3 of dilute hydrochloric acid into a 100cm3 conical flask
Set up the apparatus as shown below.
Make sure that the measuring cylinder is filled with water
Add the strip of magnesium ribbon to the flask and put the bung back onto the flask as quickly as you can and start the stop clock when bubbles appear in the measuring cylinder.

Results:

I have decided to use 0.5mol of hydrochloric acid and use magnesium ...

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Method:

Set up equipment as shown by diagram.
Take a 3cm strip of magnesium ribbon and clean it with some glass paper.
Pour 50cm3 of dilute hydrochloric acid into a 100cm3 conical flask
Set up the apparatus as shown below.
Make sure that the measuring cylinder is filled with water
Add the strip of magnesium ribbon to the flask and put the bung back onto the flask as quickly as you can and start the stop clock when bubbles appear in the measuring cylinder.

Results:

I have decided to use 0.5mol of hydrochloric acid and use magnesium ribbon because the 1.0mol of acid went down 46ml after 5 minutes and the 0.5mol only went down 10ml after 5 minutes, so the 0.5mol would be more appropriate to use because as the temperature increases, the rate will increase so if the rate became much higher than 46ml, it would be harder to calculate the correct measurement. I will also use magnesium ribbon instead of magnesium powder for the same reason but also because you need to weigh the powder to make sure it’s the same weight as the ribbon each time, which also can create a chance of an unfair test. The powder reacts quicker because the bigger the surface area, the quicker the reaction. Using the powder wouldn’t be a good idea because each time I might loose some of the gas produced trying to get the bung in. We even found this hard in the pilot before we added heat so it definitely wouldn’t be a good idea to use.

Equipment:

1 Test tube
Strips of Magnesium ribbon
10cm3 Of 0.5M hydrochloric acid
Plastic tubing
Bung
Plastic tub
100cm3 Measuring cylinder
Water
Stopwatch
Clamp

Method

We will be able to see how changing the temperature of a chemical reaction affects the speed of the reaction by adding magnesium ribbon to different temperatures of hydrochloric acid and measuring how much gas is produced every 30 seconds for 5 minutes.

Fill a medium sized tub with water and a test tube with ……… of hydrochloric acid with a concentration of 0.5M.

Fill a 100cm3 measuring cylinder with water as well and turn it upside down in the tub of water, making sure as you do it, you don’t loose any of the water in the cylinder

Place a tube under the upside down cylinder and hold the other end.

Fill a beaker with water at 30°C and put the test tube inside the beaker.

When the hydrochloric acid reaches 30°C drop the magnesium into the hydrochloric acid quickly and place the bung on the end of the tube into the top of the test tube so none of the gas escapes.

Record how much gas is collected in the measuring cylinder after every 30 seconds for 5 minutes.

Repeat the experiment changing the temperature of the hydrochloric acid to 20°C and 30°C.

Record you results in a table and then a line graph of average volumes and compare initial slopes.

Fair test: To make sure my experiment is a fair test and any variation in the results are only due to variations in the temperature I will do the following things:

I will keep all significant factors constant apart from the temperature of the hydrochloric acid. I will keep the concentration of hydrochloric acid constant because concentration is another factor that speeds up a reaction if it changes. If the concentration increases there are more particles per unit volume and collisions are more likely. There will be more collisions and thus more reactions, increasing the reaction rate. I will keep the size of the magnesium ribbon the same because surface area is another factor that could speed up the rate of a reaction, with a higher surface area it is easier for other particles to come into contact with the metal, so again this will add to the increase in the rate of reaction and will change my results maybe creating an anomaly. I will also keep the time I am measuring the amount of gas produced the same because if a metal has more time to react it will produce more gas than if it had had the same amount of time as the other reactions, creating an unfair test. I have decided to take three sets of results enabling me to take an average; this will increase reliability and create a more accurate set of results. I will take readings from 10°C to 30°C with a difference of 10°C between them.

Safety

Wear safety goggles.

Results

I did not need to carry out the third set of results because the first two results we’re clear enough to get a clear average.

From these results I could not find an anomaly so I averaged all three results.

Analysis

From my graph and results table I can see that as we increased the temperature of the hydrochloric acid, the more gas was produced and the rate of reaction increased.

Max Askwith. 11 Chemistry 1. Chemistry Coursework. 2002.