Investigating the Factors That Affect the Rate of a Chemical Reaction

Introductory information

In a chemical reaction more than two reactants are put together which makes a new product. For successful reactions to take place particles of different elements or compounds need to collide, and react together. A successful reaction happens when successful collisions take place. For successful collisions, particles must collide with enough energy to give a sufficient amount of force when colliding. From this you can see that in order for a reaction to take place, collisions between reacting particles need to happen. Activation energy represents the minimum energy needed to break bonds with reactants, with this they can react forming a new product’s’.

Two reactions colliding with enough energy new product

The reaction that I will be investigating is the reaction between hydrochloric acid and magnesium ribbon. I will use different concentrations of hydrochloric acid to see the affects, outcomes and the time taken. As the reaction proceeds I will time how long it takes for the magnesium ribbon to fully dissolve, this happens because the magnesium reacts with the hydrochloric acid.

Magnesium + hydrochloric Acid ➔ Magnesium Chloride + H2O

Mg(s) + 2Hcl(aq) ➔ MgCl + H2(g)

I will decide when my reaction has stopped by observing the magnesium ribbon and when it is out of sight and there are no more bubbles I will stop the timer.

There can be some problems with this method; there is a human eye observing it and deciding when to stop the timer and so that means it cannot be as accurate, also observing the bubbles will be hard because the bubbles are quite small. Because this method isn’t very accurate a more reliable way to decide when the reaction has stopped is observing the syringe, as when the syringe stops moving it means there is no more hydrogen being produced which means there is no more products being produced there for the reaction has stopped.

Key Factors: That could affect the rate of a chemical reaction…

A reaction takes place when there are two or more reactants trying to neutralise each other to create a new product. Reactions occur when particles of different elements or compounds collide and react together. The particles need a minimum amount of energy to make the reaction happen; this is called the activation energy. Listed below are the things that contribute in making the reaction happen quicker and slower. These key factors make successful collisions.

There are factors that speed up the process of a reaction and slow them down. The key factors that will the rate of the chemical reaction are:

Temperature
Catalyst
Concentration
Surface area

Temperature

Increasing the temperature increases the rate of reaction, this is because when a reactant has been heated, more energy then required if given to the reactant making the particles move faster. This results in more frequent collisions causing a much faster rate of reaction.

I will be using this factor in my experiment, however I will keep the ...

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There are factors that speed up the process of a reaction and slow them down. The key factors that will the rate of the chemical reaction are:

Temperature
Catalyst
Concentration
Surface area

Temperature

I will be using this factor in my experiment, however I will keep the temperature the same to ensure my test is fair. However this factor will affect my experiment because the room temperature cannot be kept constant at all times.

Catalyst

A catalyst is a substance that speeds up are chemical reaction without being chemically changed its self. Catalysts lower the activation energy, allowing more successful collisions and a faster rate of reaction

I will not be using this factor is my investigation but I will ensure my apparatus is clean accurately from any unwanted substances that may affect my experiment.

Concentration

Increasing the concentration of solutions will increase reaction rate because more particles are present in the same volume, so they are closer together and will collide more often to react. When the solution is diluted with more water the solute particles are more spread out and so less likely to collide and react. Also by having a higher concentration there is a greater chance of having more successful collisions. I will be alternating the concentrations of hydrochloric acid to see de how the rate of the reaction is affected

In a higher concentration of the reactant particles are more closely packed together. It is more likely that they will collide and a more successful collision will occur.

I will be using this factor as it is the major part of my experiment as because I will be changing the concentration of hydrochloric acid to see how the rate of reactions changes with the magnesium ribbon.

Surface area

The larger the surface area over which the reaction can occur, and the faster the reaction rate. This is because small particles have a large surface area in relation to their volume – more particles are exposed and available for collision this means more collisions take place so the reaction is faster. Oppositely large particles have small surface area in relation to their volume – fewer particles are exposed and available for collisions. This means less collisions and a slower reaction.

To ensure that my test will be fair I have to keep all these factors the same except for one, the concentration. I will have to control the temperature of the room; the particle size will be same as I will shake the substance so it will be equally diffused.

Hypothesis

I predict that the higher the concentration of hydrochloric acid the faster the reaction occurs. The lower the concentration the slower the reaction is.

Supporting information

I base this hypothesis on the collision theory as I know that concentration affects the reaction greatly. This is because when there is a higher concentration the particles are closely packed together and there are more successful collisions occurring, thus making the reaction happen quicker.

Preliminary

For my preliminary I have used various concentrations of hydrochloric acid and 4cm of magnesium

ribbon. The concentrations that I decided to experiment was 10%, 20%, 30%, 40%, 50%, 60%,

70%, 80%, 90% and 100%. The reason why I am doing a preliminary experiment is so that I know

which concentrations of hydrochloric acid to use that would make my experiment more convenient.

For the actual preliminary experiment I reacted hydrochloric acid with magnesium ribbon to see

how long it took. I did this by watching when the magnesium ribbon had stopped reacting and

disappeared. Although I was just using this method to find out how long a particular concentration

took to finish reacting I attached a glass syringe to my conical flask to observe how much hydrogen

was being produced, so that I could be prepared when it came to doing my actual experiment.

The table below shows the amount of hydrochloric acid and water I used for a certain percent and

the time taken for the magnesium ribbon to fully stop reacting.

From looking at the information from my preliminary I have decided to use the following

concentrations for my actual experiment:

20%, 40%, 60%, 80%, 100%. The reason why I have decided to use these percentages of

concentrations is because even though it shows a variety it will not be as time consuming as 10%

concentration of hydrochloric acid took 1205 seconds which was approximately 20 minutes. 10%

concentration took so long that I didn’t have enough time, there for I left it anonymous. I also

realised that even though I experiment 20% of hydrochloric acid it will still take long, there for I

decided to lower the amount of magnesium ribbon so I decided to use 3.5cm instead of 4cm.

From doing my preliminary I have decided to repeat my experiment 3 times because this will give

me a more reliable results to choose from and an average. This also will be less time consuming then

repeating it 5 times. The preliminary experiment also helped my produce a better plan because I

learnt that for 100% of concentration the reaction takes place quite quickly there for watching

the stop watch had to be done very quickly but correctly.

Plan:

The apparatus that I will be needing for experiment and why:

3.5cm of magnesium ribbons – to react with HCL

Stop watch – to measure how long it took for the magnesium ribbon to stop reacting.

Hydrochloric acid (1m) – to react with the magnesium ribbon

Measuring cylinder – to measure the concentration of H20 and HCL

Pipette – to measure smaller concentrations of H20 and HCL

Retort stand – to hold the syringe

Conical flast – for the reaction

Thermometer – to measure room temperature

Syringe – to measure the volume of hydrogen produced

Ruler – to measure 3.5cm of magnesium ribbon

Scissors – to cut the magnesium ribbon

Distilled water – to add with the concentrations of HCL

Sand paper – to sand the magnesium ribbon

1. I will firstly collect all the equipment needed for my experiment, then measure them to the

exact measurement.

I will start with 100% concentration of hydrochloric acid which will contain no distilled water and

10ml concentration. I will then measure my magnesium ribbon to 3.5cm and sand it 8 times on each

side making sure it is fair. Using the measuring cylinder and pipette I will put my hydrochloric acid

into the conical flask.

2. To ensure that the magnesium ribbon doesn’t get stuck I will coil the magnesium ribbon with a clean sterilised ruler.

3. I will then attach the syringe onto the retort stand. Then I will attach my conical flask with the syringe.

4. Because I want this test to be fair I cannot do it on my own so my partner will start the

stopwatch as soon as I drop the magnesium ribbon into the hydrochloric acid. Then I will seal the

conical flask with the cork.

5. Every 10 seconds my partner will tell my the time on the stop watch and then I will look at the

syringe to see what the volume of gas produced is. I will note this down very quickly.

6. After the reaction has fully stopped. I will empty the conical flask, then start the same process

again but for 80% concentration which is 8ml of hydrochloric acid and 2ml of distilled water. This

process will happen for all 5 concentrations.

7. After experimenting all 5 concentrations I will repeat the same process 3 times to ensure my

results are fair and reliable.

Keeping my experiment fair:

*making sure all equipment is clean from unwanted substances.

*sanding the magnesium ribbon same times on each side.

*while my partner starts stop watch, I quickly drop magnesium ribbon so it is done at the same

time.

*Use the same length of magnesium ribbon, checking it is exactly 3.5cm.

Safety issues:

*making sure I wear my goggles at all times.

*Tying hair up.

*Tuck in stalls, and stand up during experiment.

*Making sure I handle all the equipment correctly.

*If there is any spillage, quickly wiping it with paper towels.

Obtaining evidence:

100%

80%

60%

40%

To find my average number of hydrogen produced I added the 3 volumes together then divided by

3. The answer most close I decided was my average.

Investigating the Factors That Affect the Rate of a Chemical Reaction

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