Does the concentration of a solution of acid affect the rate of reaction?

INVESTIGATION- Does the concentration of a solution of acid affect the rate of reaction?

INVESTIGATION

Does the concentration of a solution of acid affect the rate of reaction?

AIM

The aim of this investigation is to find out if the concentration of an acid can affect the rate of reaction.
PREDICTION

I predict that the more concentrated the solution acid the faster the rate of reaction and the less concentrated the acid the slower the rate of reaction. This is because when there is a higher concentration, there are more particles of acid within the same amount of solution. This means there are more chances that the surface area of the magnesium ribbon (that I will be testing with) will be hit and collided by the acid particles which will reduce the time for the reaction to take place and therefore increase the rate of reaction.

FAIR TESTING

The factor that I have decided to change is the concentration of the solution of acid.

The factors I need to keep the same are: mass and length of magnesium strip, the volume of solution of acid, temperature of the solution and the surroundings, acid for solution.

I need to keep the mass of magnesium strips the same because if they were of different masses, it would be unfair if each test will have more or less material to dissolve. I also need to keep the length of magnesium the same so that the surface area can be approximately the same, it would be unfair if each test had different surface areas of magnesium to dissolve. I will keep this factor the same by cutting the same length of magnesium ribbon off the same coil.

I need to keep the volume of solution of acid the same because there will be more of the acid to continue reaction even though the concentrations are the same, so it will be unfair if one of the tests had more solution to dissolve the magnesium. I will keep this the same by using same volumes of solution.

I need to keep the temperature of the solution and the surroundings the same because the higher the temperature the quicker the particles of acid can move and collide with the magnesium ribbon and therefore increase rate of reaction, ...

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I need to keep the volume of solution of acid the same because there will be more of the acid to continue reaction even though the concentrations are the same, so it will be unfair if one of the tests had more solution to dissolve the magnesium. I will keep this the same by using same volumes of solution.

I need to keep the temperature of the solution and the surroundings the same because the higher the temperature the quicker the particles of acid can move and collide with the magnesium ribbon and therefore increase rate of reaction, so it will be unfair if one of the tests had a different temperature as it can decrease or increase the rate of reaction according to the increase or decrease of temperature.

I need to keep the same acid for the solution because different acids have different strengths; it will be unfair if I used a stronger acid because that will increase the rate of reaction. To keep this factor the same I will use hydrochloric acid only.

I am going to change the concentrations of the acid by mixing it with water. By using 2M hydrochloric acid I will take 40 ml of it to create a 2M concentration.

30ml of hydrochloric acid and 10ml of water to create a 1.5M concentration.

20ml of hydrochloric acid and 20ml of water to create a 1M concentration.

10ml of hydrochloric acid and 30ml of water to create a 0.5M concentration.

EQUIPMENT

2M Hydrochloric acid

Tap water

Measuring cylinder

12 beakers

Magnesium strip

Scissors

Ruler

Timer

PLANNED METHOD

Collect all the equipment
Measure out 10cm of magnesium ribbon and cut it. Collect 8 pieces of 10cm magnesium ribbon
Measure out 40ml of hydrochloric acid in a measuring cylinder
Pour it into a beaker
Put the magnesium ribbon into the acid solution and time how long it takes for the magnesium ribbon to completely disappear
Record
Repeat steps 3-6 with concentrations of 1.5M hydrochloric acid, 1M hydrochloric acid, 0.5M hydrochloric acid. Collect 3 of each for an average

ACTUAL METHOD

1. Collect all the equipment

2. Measure out 2cm of magnesium ribbon and cut it. Collect 8 pieces of 10cm magnesium ribbon

3. Measure out 40ml of hydrochloric acid in a measuring cylinder

4. Pour it into a beaker

5. Put the magnesium ribbon into the acid solution and time how long it takes for the magnesium ribbon to completely disappear

6. Record

7. Repeat steps 3-6 with concentrations of 1.5M hydrochloric acid, 1M hydrochloric acid, and 0.5M hydrochloric acid. Collect 3 of each for an average

There were little changes I made from my planned method. The only thing I changed was reducing the 10cm piece of magnesium ribbon to 2cm. This is because 2cm of magnesium ribbon will be faster for the limited time I have to be dissolved.

TABLE OF RESULTS

GRAPH

CONCLUSION

By looking at my graph and table of results I can clearly see that the rate of reaction increases at the concentration of acid increases. This is because where there is less time needed for the same reaction to take place the faster the rate of reaction. This agrees with my hypothesis. I have found out that the as the concentration of acid increases so does the rate of reaction. This is because in a stronger concentration, there are more acid particles within the same amount of solution and therefore the more frequent the collisions with the reactant’s surface area.

EVALUATION

By looking at my graphs and results I can see generally the trends of results are very good with a very low error range. However, I do have a single rogue result that I have taken out of the average to create a more accurate graph. My method was generally good, nothing went wrong and all went as planned. Although the drop of time needed to dissolve the magnesium ribbon was more dramatic from 0.5M to 1M, I can still clearly see that a strong negative correlation is in place.

There were some errors in this investigation. The strip of magnesium may have been uneven and even if I had cut it perfectly to 2cm, the masses may still be different; this could have caused inaccurate results.

Moreover, it is difficult to judge when the magnesium is completely dissolved. This could have caused a few seconds of inaccuracy as it is hard to determine when to stop timing.

To take this experiment further, I can use the syringe and find the gas loss of the reaction between the hydrochloric acid and magnesium. I could record the gas loss within a certain amount of time. This will be a much more accurate way of measuring this data.