Investigation of Electrolysis of Copper (II) Sulphate Solution Using Copper Electrodes

Investigate how temperature affects the rate of reaction between Hydrochloric acid and Magnesium

In this experiment, I will be investigating how changing the temperature of acid can affect the amount of gas produced in a reaction between Hydrochloric acid (HCl) and Magnesium (Mg).

The equation for the reaction is:

Magnesium(s) + Hydrochloric Acid(l) Magnesium Chloride(l) + Hydrogen(g)

Mg(s) + 2HCl(l) MgCl2(l) + H2(g)

For a chemical reaction to take place, some bonds in the reactants must be broken, and the particles must collide to gain enough energy to break these bonds. This minimum amount of energy is called the activation energy. If the activation energy is high only a small amount of particles will have enough energy to react so the reaction rate would be very small. However, if the activation energy is very low the number of particles with that amount of energy will be high so the reaction rate would be higher. An example of low activation energy would be in explosives, when they need only a small input of energy, say a change in temperature, to start their exceedingly exothermic reactions.

For this experiment, I will use hydrochloric acid (HCl), which reacts with the magnesium (Mg) to form magnesium chloride (MgCl2) and hydrogen (H2). I will be heating the hydrochloric acid at 5 different temperatures, starting from 20, 30, 40, 50, and 60oC (20°C being room temperature), and collecting the hydrogen produced. By collecting the gas, I will determine a change in the reaction rate as the acid’s temperature increases. In the solution, particles move at a range of speeds. To react, particles must collide with enough energy and in the correct orientation for bonds to be broken. By heating the acid, we ensure that the particles are moving at a faster rate, colliding more, breaking more bonds and making new ones, thus affecting the rate of reaction.

Like every experiment, there are certain factors that can affect the results. In “Rates of Reaction” there are four important factors, which will affect the experiment.

These factors are:

Temperature – an increase in temperature will make the reaction occur faster. This happens because the particles move faster when it is heated. Because the particles move faster, they would collide more, increasing the reaction rate.
Concentration – as the concentration increase, the greater and faster the reaction. This is because if the solution is more concentrated, it will increase the number of molecular collisions.
Surface area – as the surface area increases, the reaction rate will also increase. This is because there are more particles to react with the reactant in the solution.
Catalyst – this is a substance which increases the speed of the reaction, without being changed, or used up in the reaction.

There are also some variables to keep in mind when doing these experiments, which are equally important. These variables are:

The time allowed for the reaction to occur in – the longer the time, the longer the magnesium has to react with the hydrochloric acid.
The quantity of acid – the more the acid, the more the magnesium has to react with. But use too little and the magnesium won’t have enough to finish the reaction
The equipment used
The amount of magnesium used.

This is a preview of the whole essay

In this experiment, I am looking at how increasing the temperature can affect the rate of reaction of magnesium. I will measure this by measuring the Hydrogen given off each test. I will change the temperature of the Hydrochloric acid at 5 different temperature points while keeping everything else the same. I will easily control the amount of acid, the surface area, the time, the amount of magnesium, and the equipment. I have chosen to use 25ml of acid because it is just the right amount for the magnesium to react to completely. I am going to use 2cm of magnesium because it seems well proportioned to the amount of acid, as there is enough to react with the acid and enough for time given. The time I have chosen is 30 seconds this is because, again, it seems well proportioned to the rest of the experiment. 30 seconds allow the magnesium to fully react with the Hydrochloric acid before the reaction stops and starts giving the same results. The temperatures I am going to use are 20, 30, 40, 50, and 60°C. I will use these temperatures because it seems like a good range to get a wide variety of results. I will start on 20°C naturally because it is room temperature.

Prediction:

I predict that, as the temperature increases, the speed of reaction will increase. Therefore, the gas will be produced faster and more will be produced in 30 seconds. I believe this because most chemical reactions happen faster when the temperature is higher. At higher temperatures, particles move around faster, colliding more, which makes it easier for them to break bonds, make new ones, thus reacting together. Usually, rises of 100oC will double the rate of reaction. My prediction can be supported by the “Collision Theory”, which describes how the rate of reaction increases as the temperature increases.

The “Collision Theory” states: As the temperature rises, more energy is given to the particles so their speed increases; this increases the number of collisions per unit of time.

The “Particle Theory” can also be used to support my prediction.

It states: for chemical reactions to occur, there must be a collision at a certain velocity and at a certain angle. Also, the factors that affect the rate of a reaction are the surface area of the solid reactant (if there is a solid reactant), the concentration of the aqueous reactant(s), the presence of catalysts and temperature.

Method:

The equipment that will be used in the experiment:

Bunsen burner: to heat the acid
Conical flask: to heat the acid in
Bung: place securely in the flask during the reaction to collect the gas
Bowl: to put the water in
Tap water: to put into the bowl and measuring cylinder for gas collecting purposes
Hydrochloric Acid (25ml): reacts with Magnesium
Magnesium (2cm): reacts with acid
Tongs: to hold the flask above the flame
Thermometer: to control the temperature
Stop Watch: to time the reaction
Measuring Cylinder: to measure the Hydrochloric acid and to collect the gas
Ruler: to measure the magnesium
Pen: to mark measuring points on the Magnesium
Paper towels: for safety and for cleaning and drying
Heat Mat: for safety
Goggles: for safety

I will first lay out all the apparatus I need. I will set them up as shown

Preparation:

I will first draw out the tables I am going to use to record my results in and note down all the measurements I am going to use.

I will use a ruler to accurately measure the Magnesium and with a pen, I will mark every 2cm on the Magnesium ribbon, then cut them up according to the markings as accurately as possible. 25ml of Hydrochloric acid (HCl) will be measured using a small measuring cylinder, each unit measuring 5ml. By using a small measuring cylinder, I ensure that I get more accurate measurements than using a large one with such small amounts of acid, which will then be poured into a conical flask. I will fill a bowl and a large measuring cylinder full of tap water, and place the measuring cylinder upside down into the bowl, which is also full of water. To do this, I will block the mouth of the measuring cylinder tightly with the palm of my hand, and gently tip it upside down, then carefully placing it into the bowl of water. I will be sure not to let any water escape from the measuring cylinder while doing this, as this would create inaccuracies in the experiments. I will then put the tube of the bung into the cylinder that is upside down, so that I can measure the gas given off as it travels up the tube, and into the cylinder. I will do the experiment as accurate as possible in each experiment to make it a fair test. I will do this by measuring exactly 25ml of Hydrochloric acid each test. I will also thoroughly rinse the flask after each experiment, and dry it after with a piece of paper towel on the end of a pencil so that no water will dilute the acid in the next experiment. The Magnesium will also be measured and cut accurately, so no test will have a larger amount of Magnesium to react with the acid. The Magnesium will also be used as whole pieces as splitting the 2cm pieces into two 1cm pieces will increase the surface area and change the results. I will use the same equipment and I will carry out my experiment around the same area of the room for each 20oC experiment, as this will reassure that the room temperature is around the same oC.

Experiment:

The temperatures I am going to use are 20, 30, 40, 50, and 60°C. I will use this range because I think that I will get some varied results. I have chosen to start at room temperature, which is 20°C, as this seems like a reasonable temperature to start on. For every experiment that is not 20°C, I started by heating up the Hydrochloric acid (HCl) to the temperature needed, by using a thermometer that was placed into the acid. To heat the Hydrochloric acid, I placed the conical flask securely in a pair of tongs and hovered it over a small blue flame. I was prepared to cool the acid if it got too hot, and try and get the exact temperature I need. Once heated, and with a stopwatch at hand, I (very quickly) put the Magnesium into the Hydrochloric acid, placed the bung securely on top, and started the stop watch as soon as the Magnesium hit the acid. I collected the Hydrogen gas (H2) for 30 seconds and quickly pulled out the tube when the time was up. I then stopped the watch and recorded down the amount of gas collected in cm3. The 20oC experiment was done in exactly the same way but was not be heated at all. After the experiment, I thoroughly rinsed out the conical flask so no extra acid or Magnesium would affect the results of the future experiments. I then repeated the experiment 3 times to ensure that I have plenty of data to draw reliable and accurate conclusion. This will also give me a total average of the final results and to draw an accurate graph.

Safety: I will have to do a few things in order to make my experiment safe. Firstly, all stools should be tucked under the table, and bags should be out of the way so no one will trip over them. I will have to careful when the Bunsen burner is on, and make sure the flame is visible when not in use (this is so other people can see them, and is crucially important when it’s a small blue flame, because they’re completely invisible). I will also make sure that the Bunsen burner is placed on a heat mat. Goggles should be worn throughout the experiment (especially when heating acid over a flame). After the flask is heated, I will use a folded up piece of paper towel, and wrap it around the neck of the flask and hold it tightly (to make sure I don’t find it too hot and drop it).

After the experiments, I recorded down the results in tables as shown below. I repeated the experiment 3 times in 3 tables and worked out an average result, which is shown in the last column of the table.

To find the average of the 3 experiments, I added each volume of gas collected for each temperature, and divide it by 3.

20 oC: 18 + 14 + 17 = 49 30 oC: 20 + 25 + 30 = 75 40 oC: 28 + 25 + 32 = 85

49/3 = 16.3 75/3 = 25 85/3 = 28.3

50 oC: 32 + 20 + 40 = 92 60 oC: 34 + 27 + 37 = 98

92/3 = 30.7 98/3 = 32.7

After finding the average results of how temperature can increase the Rate of Reaction, I could then draw a graph to show this.

The table shows clearly that the Volume of Gas collected (cm3) increases as the temperature increases. Four points in the graph have a line of best fit with positive correlation. This clearly shows that there is a direct relationship between temperature and the rate of reaction; they are proportional to each other. This proves both particle, and collision theory reliable. The particle theory says that for chemical reactions to happen, there must be collisions, but there are also factors that affect the rate of reaction. In this experiment, the factor that I concentrated on was temperature, and from the graph, I was able to draw the conclusion that temperature does, in fact, affect the rate of reaction, in that when the temperature is higher, the reaction takes less time, as there are more collisions between the particles because of the temperature rise. Four points in the graph have a line of best fit with positive correlation. This clearly shows that there is a direct relationship between temperature and the rate of reaction; they are proportional to each other. This proves that both theories are dependable, and it determines my prediction correct.

At 20oC, the reaction took longer to occur, as the hydrogen was produced very slowly. This was because there was not much heat to provide the particle with enough energy for a fast reaction. A the temperature increased, the graph shows that more gas was collected, verifying that the rate of reaction must have increased for most gas to be collected in the same amount of time.

Evaluation:

I think my results prove to be quite reliable, and also prove both theories reliable. This tells me that my experiment was a successful one although I could have improved on my method. Instead of heating the Hydrochloric acid directly over a small blue flame, I could have put the acid into a test tube and heated it in a water bath, where the water would be heated in a beaker, settled on top of a tripod and gauze. That would be a much safer option of heating the acid. Other than the method, I think that the experiment was quite successful. The graph shows this, as the line is almost a perfect curve. The graph shows no anomalous results, however, when you look at the result tables, we see that there were in fact quite a few anomalies, where the volume of gas collected doesn’t increase with the temperature. These anomalies could be fixed by improving certain factors and accuracy within the experiment. Throughout the experiment, certain uncontrolled factors could have affected the experiment. Such factors could include the concentration of the acid. Even though the conical flask was dried of quite thoroughly, water residue could still temper with the concentration of the acid. In a need for greater accuracies, I would use a new conical flask every test to ensure that there is nothing that could affect the concentration of the Hydrochloric acid. One major factor that could have affected the results is that, the experiment was carried out in a series of lessons, on different days, and in different times of the day. This factor could really affect the room temperature experiment, as the temperature would change slightly every time. To overcome this problem, instead of starting the experiment on room temperature, I would start it at 30oC. By doing this, the difference in room temperature would not matter, and this would solve some anomalies in this area. By doing the experiment throughout different days, many variables could have changed and that would affect the results dramatically, variables such as the strength of acid and the purity and cleanliness of the magnesium. To overcome these problems for a greater accuracy, the same stock of Hydrochloric acid should be used every experiment, and the same ribbon of magnesium. The magnesium should be new, as substances on it could tamper with the results.

I did the experiment as accurate as possible by measuring accurately and sensibly, and made sure that the same equipment was used throughout the experiments. When tipping the cylinder upside down, I made sure that no water escaped so there was no air in the measuring cylinder before the experiment.

The experiment was frankly, quite boring but it helped me understand the rate of reaction more, and also particles and collisions. It helped me understand how so many factors could affect the rate of reaction, and if I were to investigate “rate of reactions” to more depth, I would try investigating how the other four major factors would affect it. These factors include the concentration of the acid, the surface area of the solid, or even adding a Catalyst.