Factors That Affect the Rate of a Chemical Reaction.

GCSE Science

Observation on:

Factors That Affect the Rate of a Chemical Reaction

Name: Fahad E. Al Butairi

Badge: #277045

Instructor: Mr. Fawaz

Abstract:

It’s useful to be able to predict whether an action will affect the rate at which a chemical reaction proceeds. There are several factors that can influence the rate of a chemical reaction. In general, a factor that increases the number of collisions between particles will increase the reaction rate and a factor that decreases the number of collisions between particles will decrease the chemical reaction rate. As we will see in the following experiments there are different types of factors that will affect the rate of a chemical reaction.

Introduction:

What is a Chemical Reaction?

A chemical reaction occurs when substances (the reactants) collide with enough energy to rearrange and form different compounds (the products). This type of collision is called a successful collision, and the energy used to form these compounds is called the Activation Energy.

What is the Activation Energy?

Activation energy is the amount of energy required for the reactants to successfully react. The reactants need a certain amount of energy, any extra energy increases they’re chance of a successful collision.

What is the rate of a chemical reaction?

The rate of a chemical reaction is a measure of how quickly a reaction proceeds with time.

The reaction rate is a quantity that defines how the concentration of a reactant or product changes with time. It depends on four main factors that can change it: Surface area, concentration, temperature, catalysts.

Predictions:

I predict that the rate of reaction should increase as I increase the surface area between the reactants, because there will be more collisions between the reactants’ atoms which will increase the rate of reaction.

I predict that the rate of reaction should increase as I increase the concentration of the acid, because higher concentration means more reacting atoms which will increase the number of collisions and increase the rate of reaction.

I predict that the rate of reaction should increase as I increase the temperature, because increasing the temperature of the reacting atoms means supplying them with more kinetic energy which will make them move faster and collide more with each other and that will of course increase the rate of reaction.

I predict that the rate of reaction should change as I add catalysts. Catalysts are substances that can influence the reaction by two ways; either to increase, or decrease, the rate of reaction. It can increase it either by weakening the chemical bonds that are needed to be broken, which means less energy needed for the reaction to take place, or by holding one of the reactants and so the other reactant can collide easily with it. The catalyst can also decrease the rate of reaction by acting as a barrier that keeps the atoms of the reactants from colliding.

Materials and Equipment:

Equipment:

Magnetic stirrer with bar.
Conical flask.
Delivery tube with stopper.
Gas-collection tube.
Water trough.
Laboratory stands.
Utility clamps.
Measuring-cylinder (50ml).
Micro-spatula.
Stop-clock.
Water bath.
Polystyrene cup.

Materials:

- 1.00M hydrochloric acid.

0.20M hydrochloric acid.

- Magnesium ribbon (10 cm strips).

Zinc metal (mossy).
Steel wool.
0.20M solutions of copper (II) nitrate; nickel (II) nitrate and cobalt (II) nitrate; iron (II) ammonium sulfate(s).
Distilled water.

Methods and Procedure:

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Materials and Equipment:

Equipment:

Magnetic stirrer with bar.
Conical flask.
Delivery tube with stopper.
Gas-collection tube.
Water trough.
Laboratory stands.
Utility clamps.
Measuring-cylinder (50ml).
Micro-spatula.
Stop-clock.
Water bath.
Polystyrene cup.

Materials:

- 1.00M hydrochloric acid.

0.20M hydrochloric acid.

- Magnesium ribbon (10 cm strips).

Zinc metal (mossy).
Steel wool.
0.20M solutions of copper (II) nitrate; nickel (II) nitrate and cobalt (II) nitrate; iron (II) ammonium sulfate(s).
Distilled water.

Methods and Procedure:

Diagram 1: The diagram above shows how to assemble the apparatus for the experiment.

Part I - The Effect of Surface Area:

The apparatus was assembled as shown in the diagram above.

20 ml of 0.2M HCL acid was taken in a measuring cylinder. The diluted acid was put into a conical flask, the magnetic stirrer bar was added and the solution was allowed to stir for a few seconds.

A 10 cm piece of magnesium ribbon was taken; then it was placed in the conical flask.

The flask was closed immediately with the stopper on the delivery tube and the stopwatch was started.

The volume of gas produced each minute was recorded in Table 1 over a period of 10 minutes.

Steps 1-5 above were repeated except, the magnesium ribbon was folded so that the exposed surface area was reduced to about half.

Steps 1-5 above were repeated except, the magnesium ribbon was folded so that the exposed surface area was reduced to about a quarter.

Finally at the end of the experiment, the magnesium ribbons were thrown into the waste bin and the conical flasks were all washed.

Part 2 - The Effect of Reactant Concentration:

The apparatus was assembled as shown in diagram above.

20 ml of 0.2M HCL acid was taken in a measuring cylinder. The diluted acid was put into the conical flask, the magnetic stirrer bar was added and the solution was allowed to stir for a few seconds.

A 10 cm piece of magnesium ribbon was taken; it was cleaned with some iron wool and placed in the conical flask.

The flask was closed immediately with the stopper on the delivery tube and the stopwatch was started.

The volume of gas produced each minute was recorded in Table 2 over a period of 10 minutes.

Steps 1-5 above were repeated except, in step 2 18 ml of acid was taken and added to 2 ml of distilled water in the conical flask (i.e. a concentration of 0.18M acid).

Steps 1-5 above were repeated except, in step 2 16 ml of acid was taken and added to 4 ml of distilled water in the conical flask (i.e. a concentration of 0.16M acid).

Steps 1-5 above were repeated except, in step 2 14 ml of acid was taken and added to 6 ml of distilled water in the conical flask (i.e. a concentration of 0.14M acid).

Steps 1-5 above were repeated except, in step 2 12 ml of acid was taken and added to 8 ml of distilled water in the conical flask (i.e. a concentration of 0.12M acid).

Finally at the end of the experiment, the magnesium ribbons were thrown into the waste bin and the conical flasks were all washed.

Part 3 - The Effect of Temperature:

The apparatus was assembled as shown in diagram above.

10 ml of 0.2M HCl acid was taken in a measuring cylinder and 10 ml of distilled water was added (i.e. a concentration of 0.10 M acid).

The diluted acid was put into the conical flask the magnetic stirring bar was added and the solution was allowed to stir for a few minutes to allow its temperature to come to room temperature. The temperature was recorded in table 3.

A 10 cm piece of magnesium ribbon was taken; it was cleaned with some iron wool and placed in the conical flask.

The flask was closed immediately with the stopper on the delivery tube and the stopwatch was started.

The volume of gas produced each minute as recorded in Table 3 over a period of 10 minutes.

Steps 2-6 above were repeated except a conical flask with 0.10M HCl that had been cooled in some ice was used.

Steps 2-6 above were repeated except a conical flask and acid solution were heated in a water bath to about 92°C.

Finally, Steps 2-6 above were repeated again except a conical flask and acid solution were heated in a water bath to about 56°C.

At the end of the experiment, the magnesium ribbons were thrown into the waste bin and the conical flasks were all washed.

Part 4 - The Effect of Catalysts (Metal Ions):

The apparatus was assembled as shown in diagram 1.

25 ml of 1.0M HCl acid was measured out with a measuring cylinder and was put in a conical flask. The magnetic stirrer bar was added and the solution was allowed to stir for a few seconds. A small lump of zinc was taken and placed in the conical flask.

The flask was closed immediately with the stopper on the delivery tube and the stopwatch was started.

The volume of gas produced each minute was recorded in Table D over a period of 10 minutes.

Steps 2-4 above were repeated except that about 20 drops of 0.2M copper (II) nitrate solution were added to dilute the acid in step 2.

Steps 2-4 above were repeated except that about 20 drops of 0.2M cobalt (II) nitrate solution were added to dilute the acid in step 2.

Steps 2-4 above were repeated except that 2-3 crystals of iron (II) ammonium sulfate were added to dilute the acid in step 2.

Steps 2-4 above were repeated except that about 20 drops of 0.2M-nickel (II) nitrate solution were added to dilute the acid in step 2.

Finally at the end of the experiment, the magnesium ribbons were thrown into the waste bin and the conical flasks were all washed.

Data and Graphs:

Analysis and Conclusion:

The results are clear, reliable and relevant. It is believable because they corresponds in clearly with the given theories and principles.

The rate during the reaction does not stay constant, it changes throughout the reaction, and its greatest is at the start of the reaction but gets slower as the reaction proceeds. I think this mainly to do with the fact the longer the reaction has taken place the more of the reactants react leaving fewer reactants with less chance of reacting. A successful collision is when the reactants react they successfully collide with each other. The chance of a successful collision can be increased or decreased by using many different factors. I’ve been able to analyze the data given and graphs with the reference help from chapter 22, section 22.1 of Merrill’s Chemistry Book, I’ve managed to conclude the following:

Surface Area:

From the first graph, we can see that the greater the surface area is, the rate of the chemical reaction will also greatly increase. This is proven to be true, for the greater the surface area of the reactants the more particles there are available for a successful collision.

Temperature:

Temperature alters the rate of a reaction by supplying the reactant particles with more kinetic energy, the more kinetic energy the reactants have the faster they move around increasing the chance of having a successful collision. As we can see from graph 3, the rate of the reaction at a temperature of 60°C increased greatly over the rate of reaction at a temperature of 40°C. In reality this is proven to be correct, for the greater the temperature the faster the rate of a reaction.

Catalysts:

A catalyst is a substance that changes the rate of a chemical reaction but remains chemically unchanged itself. As we can see from the graph 4, the cobalt ions manage to make the big difference in speeding up the rate of the chemical reaction, unlike the rest of the catalysts. This could be because of the each catalysts different electron configurations, which would give us different properties for each catalyst and that could alter the rate of the chemical reaction.

Concentration:

Concentration affects the rate of a reaction because the higher the concentration of particles the greater the chance of a successful collision. The general trend is that the concentration is directly proportionate to the rate of the reaction. As we can see from graph 2, as I have stated before as the concentration increases the rate of the chemical reaction greatly increases also.

Improvements:

If I was to do this experiment again I would probably make it more accurate by:

- Using a Burette to measure the amount of gas given off. This would measure a lot more accurately the amount of gas given off.

- Using smaller particles of magnesium and zinc and similar weight. So I could match up surface area and weight more accurately each time.

- Checking if the concentration of acid is proportional to the rate of the reaction.

Taking control of the stopwatch. There is lots of room for human error here but mainly this can be somewhat neglected.

Using some kind of a gadget that can start the stopwatch in the same instant of the first bubble when appears.

Using more purified distilled water will enhance the experiment.

In this experiment, Mg was used regardless of its real length. It is believed that applying the experiment with measured lengths of Mg ribbons may provide us with results and proofs that will drive to discover a certain pattern that will finally lead us to a fixed law (equation).

Literature Cited: