Investigating how varying the concentration of Hydrochloric acid affects the rate of reaction.

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Chemistry Investigation- Rates of Reaction

 Introduction:

For two substances to react in the first place their particles must meet and collide. They must collide with enough force, sufficient amount of energy (called activation energy that is the energy needed to start a reaction) and in the right direction so a reaction can successfully occur. The rate of reaction is dependent on the number of successful collisions taking place. Some reactions are instantaneous, while some, like the metaphoric rock take millions of years. The rate of reaction can be calculated as the amount of product formed or used up per second.

Title/ Aim:

 Investigating how varying the concentration of Hydrochloric acid affects the rate of reaction.

Prediction/hypothesis:

I predict that calcium carbonate and hydrochloric acid will react together and that the higher the concentration the faster the rate of reaction. This is because as you increase the concentration you increase the number of particles in turn increasing the chance of particles colliding successfully. So I predict if the concentration is doubled then the rate of reaction is doubled.

Apparatus:

 The following is a list of the equipment needed to carry out the practical:

Conical Flask

Delivery tube

A narrow measuring cylinder to measure a smaller volume

A large measuring cylinder to measure the collected gas

A normal measuring cylinder for a larger volume

Tub of water

Weighing scale

Stop watch

Hydrochloric acid solution- 4 moles

Marble chips to represent Calcium Carbonate

Water bath

Bunsen burner

Thermometer

Method:

Diagram illustrating the layout of experiment:

Firstly, I will set up the apparatus as the diagram above illustrates. I will then fill the tub with water and then measure 50 cm³ of acid and pour it into the conical flask. Then I will weigh the mass of 3 marble chips to a total of exactly 7 grams and insert the bung to prevent spitting from the reaction. The reaction will cause the water to be displaced by the gas produced. I will then place the flask on the burning Bunsen burner and using the thermometer, regularly check that the temperature is always 27°C. If the temperature is lower then I will lower the flame, however if the temperature  From the first bubble ( signifying the reaction has started)  I shall start timing how long it take for 100cm³ of carbon dioxide to be collected and then record it. I will then repeat the experiment except having different percentages of concentration by: subtracting the concentration by 10cm³ and replacing it with water and making sure that the total volume will always be 50cm³. I will then finally repeat the whole experiment 3 times in order for the experiment to be fair. Then I will plot a graph of the averaged results.

Preliminary work:

Before doing the actual practical I did a trial to ensure that the method that I was going to use for the practical was appropriate, accurate and reliable.

From the preliminary I observed that if I used really small marble chips or too many it would cause a fast reaction and be too difficult to record. This is because the smaller the chips, the larger their surface area is (surface to volume ratio) therefore the reaction takes place faster because more particles are successfully colliding. So it makes it difficult to quickly note down. To solve this problem I used only 3 large marble chips that had a total mass of 7 grams.

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Below are the results of my preliminary work:

The results that I have obtained are appropriate and the time taken steadily increases without any anomalies. Thus, the method demonstrated above will be the one I will use in the actual practical

Range of measurements:

My preliminary helped affirm the range of measurements that I was going to use. I am going to vary the concentration of hydrochloric acid to 5 different concentrations. I will do this like I mentioned before by taking 10cm³ of hydrochloric acid away each time and replacing it ...

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