Rates of reactions between HCL and magnesium ribbon.

Rates of reactions between HCL and magnesium ribbon

Aim

I plan to investigate the effect of concentration of acid, in the reaction between dilute hydrochloric acid and magnesium ribbon. The rate of a chemical reaction is a measure of how fast the reaction takes place. It is important to know that a rapid reaction is completed in a short period of time. Some reactions are very fast, for example; the formation of silver chloride precipitates when silver nitrate and hydrochloric acid solutions are mixed. In this investigation I will test different concentrations of acid reacting with magnesium.

Prediction

My prediction is that as the concentration of the hydrochloric acid increases, the time taken for the magnesium to disappear decreases. I predict that when the concentration of the hydrochloric acid doubles, the rate of the reaction doubles.

Linking prediction to theory
Reaction rate and concentration.

The collision theory describes how the rate of reaction increases (the time taken for the magnesium ribbon to disappear when it is reacted with hydrochloric acid) when the concentration of HCL increases. As the reaction continues, the concentration of the reacting substances decreases and so does the rate of reaction. The reaction is speeded up if the number of collisions is increased. The higher the concentration of HCL you use, the less time it takes for the magnesium to disappear and so the rate reaction increases. 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 the activation energy is very low the number of particles with that amount of energy would be so high, so start, so the reaction rate would be higher.

Apparatus

Hydrochloric acid(3 mole)
Water(to dilute acid)
10ml testube
magnesium(2cm long)
stop clock(sensitivity 1/10s)
beaker

Method

To get the amount of magnesium and the amount of hydrochloric acid to use in the situation, we have to use an excess of acid so that all of the magnesium disappears.

An equation for the reaction:
Magnesium + hydrochloric acid >magnesium chloride + hydrogen
Mg(s) + 2HCL(aq)>Mgcl2(aq) + H2(g)
1mole 2moles 1mole 1mole

So we can say that one mole of magnesium reacts with 2 moles of hydrochloric acid. Throughout the experiment, we diluted the acid solution using water, as we did this the concentration of the acid decreased. Then 8ml of acid and 2ml of water solution on the magnesium, measured time taken for magnesium to disappear using stop clock. Then 7ml of acid and 3ml of acid, repeated as above. This way the rate of reaction(the time taken for the magnesium to disappear) was measured accurately for a fair test.

Results
The results for the time taken for magnesium to disappear when it is placed in different concentrations of acid are summarised below.

Analysis of results

From the results in the table and the graph we can see a steady increase in the rate of reaction as the concentration of the acid decreases. This complies with my prediction. The graph shows that there is an increase in the rate of reaction as the concentration increases because the graph has it's largest gradient or it is steepest at this point. When the graph was made into 1/time the result should have been a straight line graph but it did not turn out this way even though concentration~1/time. This 1/time graph could be wrong because of inaccurate results so there seems to be no relationship between the concentration graph and the 1/time graph. We can see from the rate of reaction graph that when the concentration roughly doubles from (1.8 moles to 3 moles) the rate of the reaction doubles (from 25 to 60 seconds). Also we can see that as the reaction continues the concentration of the reactants decrease and so does the rate of the reaction as we can see the decreasing gradient on the graph steadily falling and coming to a stop when the reaction is complete and the magnesium has completely disappeared.

Conclusion

I can conclude that if you double the concentration of the acid the reaction rate would also double, this is because the ions are closer together in a concentrated solution. The closer together they are, the more often the ions collide. The more often they collide, the higher the chance of a reaction between the magnesium and the hydrochloric acid. Also because there are more particles in the solution which would increase the likelihood that they would hit the magnesium so the reaction rate would increase. The graph gives us a good device to prove that if you double the concentration the rate of reaction doubles. If you increase the number of particles in the solution it is more likely that they will collide more often. In the reaction, when the magnesium hit the acid, it fizzed and produced many bubbles it was silver in colour (which is one of magnesium's physical properties silvery
white metallic element), the activation energy of a particle gets higher with heat, the particles which have to have the activation energy are those particles which are moving, in the case of magnesium and hydrochloric acid, it is the hydrochloric acid particles which have to have the activation energy because they are the ones that are moving and bombarding the magnesium particles to produce magnesium chloride. The graph for 1/time had the form of an s curve and it did have some relationship with the other graph.

Evaluation

There are many reasons why our results for the 1/time graph did not prove the point that concentration~1/time, such as

1. When the reaction takes place bubbles of H2 are given off, which might stay around the magnesium, which therefore reduces the surface area of the magnesium and so the acid cannot react properly so this affects the results.

2. We could have controlled factors in the investigation better (e.g. the stirring of the solution because if this is not done properly it can lead to incorrect results).

3. Using larger concentrations of acid would give a bigger more accurate conclusion instead of just using 10ml test tubes use 1litre test tubes, this way graphs would be more spaced out and give an accurate form or curve.

Investigating the Rate of Reaction Between Magnesium Ribbon And Hydrochloric Acid Safety- must alway

From www.courseworkbank.co.uk

Search over 30,000 pieces of coursework at .

Investigating the Rate of Reaction Between Magnesium Ribbon And Hydrochloric Acid Safety- must alway

Safety- must always wear safety glasses and we should be very careful not to drop any acid.

This is a preview of the whole essay

Investigating the Rate of Reaction Between Magnesium Ribbon And Hydrochloric Acid Safety- must alway

From www.courseworkbank.co.uk

Search over 30,000 pieces of coursework at .

Investigating the Rate of Reaction Between Magnesium Ribbon And Hydrochloric Acid Safety- must alway

Safety- must always wear safety glasses and we should be very careful not to drop any acid.

Fair test- we must make sure that we use the same size, amount and roughly the same mass of magnesium, this is because we want to keep the ribbon roughly the same all the way through the experiment so that it will be a fair test and the results we be in relation to each other, otherwise the results will be completely different to what we will expect and it will ruin the experiment. We must also take our readings at the same intervals throughout the experiment i.e. I will take a reading every fifteen seconds for all of my experiments.

I predict that the more concentrated the acid the quicker the reaction will take place, because the more concentrated the acid is then it will make the magnesium react faster and more hydrogen will be given off in a quicker time.

Equipment- we will need a boiling tube, Magnesium Ribbon, hydrochloric acid, water, and a stopwatch.

Method When doing my experiments I will use the same procedure throughout. Once I have set up the apparatus I will measure out 5cm3 of acid in a measuring tube and then pour it into a boiling tube with 45 cm3 of water. Then I will be ready with the stopwatch and then quickly drop in the ribbon into the acid, and start the stopwatch. This must all be done in a very short space of time. I must record the results in a table and then write it up neat later. The factors, which may affect how well the experiment works, are how quickly the ribbon is placed in and the stopwatch pressed. Although this is a factor it is not really a major factor that will affect the end results, and as long as the time it all takes is kept constant throughout then it should not matter too much. I will then repeat the experiment for the rest of the concentrations. I will then repeat the whole experiment again and take the average of both results for each concentration. Other factors are what kind of water to use for dilution, I could either use water from the tap which is not very pure or it may be too hot or too cold, or I could use distilled water. Tap water may have some things in it that may affect the results. The temperature also could affect the experiment because if heat is applied then the particles would move around more and affect the. I think I will need one result for each concentration and later if I need to repeat any experiments I can do. To get the best results I need to use the equipment in the best possible way. Results Evaluating Evidence I think that the experiment went very well. This is because I got all the results that I wanted and they look very good. The results were very accurate and so I am able to make a good conclusion. From looking at my results I can see that there were no poor results, which was a good thing, and it proves that everything went very well. Even though the experiments went very well I decided to repeat one concentration of acid again just to see if I could repeat the experiment and get roughly the same results, which is what I did do, and these to went very well. There was no real source of error in the apparatus along as it all was working well and the way it should have been. The only possibility was if the temperature of the acid had changed from when we did the first reading to the finish i.e. from when we did the first experiment, the acid hopefully would have been the same temperature. From looking at my results and graph I am able to conclude that the more concentrated the acid the quicker the reaction happened. As we look at the graph we can clearly see that in all five results at the beginning the reaction happened more quickly than at the end where we can see that it started to tail off. Before I did the experiments I made some predictions they were that the more concentrated the acid was the quicker the reaction. This was completely correct because what I thought would happen did.

Reaction between HCl and Mg

In the reaction between hydrochloric acid and magnesium ribbon, the hydrochloric acid will dissolve the magnesium and produce hydrogen gas. All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products. In my experiment the reactants are hydrochloric acid and magnesium ribbon. The chemical reaction takes place when the magnesium ribbon is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula equation for this experiment is:

Mg + 2HCl (r) MgCl2 + H2

Magnesium + Hydrochloric acid (r) Magnesium Chloride + Hydrogen

The rate of reaction between the product and the reactant will increase or decrease depending on certain factors. The factors that may affect the rate of reaction are:- temperature of the Hydrochloric Acid, mass of the magnesium ribbon used, concentration of the Hydrochloric acid, surface area of the magnesium ribbon used
All of these factors will change the rate of reaction because of the Collision Theory. This is a theory that is used to predict the rate of a reaction. The Collision Theory is based on the idea that for a chemical reaction to take place, it is necessary for the reacting particles to collide with each other with enough energy to break or form new bonds between the other particles, which is called a successful collision. If when they collide and they do not have enough energy to break or form new bonds then they will simple bounce of each other, causing an unsuccessful collision.

Scientific Knowledge

"When a chemical reaction occurs, the particles which combine need to meet up with each other (collide) so that they can swap or share electrons. If you want to speed up a reaction, you need to get these particles to hit each other more frequently." (www.revise.it)

? ?
" If the solution is made more concentrated it means there are more particles of reactant knocking about between the water molecules, which make collisions between the important particles more likely." (GCSE Double Science Revision Guide)

Method

Fair Test
In order to keep my experiment a fair test I will have to make sure that I keep the following factors the same:- volume of acid used (cubic centimetres), surface area of the magnesium, length of magnesium. I will also have to make sure that the gas syringe is correctly connected and that it is placed quickly and tightly enough so that no hydrogen gas escapes. To make sure that all my results are as accurate as possible I will do each experiment three times and then take an average to prevent any anomalous results affecting the end conclusion in a big way.

Safety
The safety of this experiment is very important. The things that I will need to do to keep my experiment safe for myself and other students around me are as follows:- Wear safety goggles as I am using hydrochloric acid which can irritate the skin, Care to eyes and the skin besides all the other people is always vital and necessary, Care in using glassware since it is sharp when broken and can cut skin. Safe disposal of reagents and laboratory chemicals, Care when returning all used glassware and equipment at the end of the experiment

Plan
The experiment will be done using the equipment shown above. The acid will be measured in a measuring cylinder and then put into a conical flask. The water (if necessary) will be measured in the same way and added to the same conical flask as the acid. When I have set the gas syringe up in a clamp ( see diagram), I will cut a piece of magnesium ribbon to 5cm long. To make sure that all the gas given off is collected, I will ask some-one else to start the stop-watch as soon as the magnesium ribbon is in and the bung to the conical flask placed in the top. I will then time for 2 minutes and take a reading of the gas every twenty seconds. I will use six concentrations for this experiment and they will be:-
25ml acid : 0ml water
20ml acid : 5ml water
15ml acid : 10ml water
10ml acid : 15ml water
5ml acid : 20ml water
0ml acid : 25ml water
I will record the results in a table like the one shown below:

AMOUNT OF GAS COLLECTED
Time (s) Experiment 1
(ml) Experiment 2
(ml) Experiment 3
(ml) Average
(ml)
20
40
60
80
100
120

Prediction

I predict that the higher the concentration of the acid, the faster the rate of reaction will be. I predict this because I know that the higher the concentration of the acid, the greater the number of acid molecules present in that volume. This means that there are more acid molecules colliding with the particles on the surface of the reactant ( magnesium) thus increasing the rate of reaction.

Hypothesis

What are the factors Affecting the rate of reaction between magnesium and Hydrochloric acid?I

predict that as the temperature increases, the speed of the reaction will increase therefore the gas will be produced faster. I believe this because most chemical reactions happen faster when the temperature is higher. At higher temperatures molecules mover around faster, which makes it easier for them to react together. Usually, rises of 100C will double the rate of reaction.

Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.

What factors affect the rate of reaction between magnesium ribbon and hydrochloric acid?

GCSE CHEMISTRY COURSEWORK

This chemistry coursework requires an investigation to see how long it takes for magnesium ribbon to be eaten away by hydrochloric acid.

Before starting the investigation, I decided to do some research about magnesium and hydrochloric acid.

Magnesium is a light, shiny grey metallic element, symbol Mg, atomic number 12, found in group two in the periodic table. It is quite reactive giving vigorous reactions towards acids. It is one of the alkaline earth metals, and the lightest of the commonly used metals. It is used in alloys, flash photography, flares, fireworks and flash bulbs because it burns vigorously in air with a bright white light. Magnesium reacts with steam to release hydrogen and it also burns in carbon dioxide gas.
Hydrochloric acid, HCl, is a solution of hydrogen chloride (a colourless acidic gas) in water. The concentrated acid is about 35% hydrogen chloride and is corrosive. The acid is a typical strong, monobasic acid forming only one series of salts, the chlorides. Like most acids, it releases hydrogen ions when it is added to water and certain metals, and has a pH of less than 7. Hydrochloric acid is a common laboratory acid.

Extracts from: a chemistry coursework from an Internet source and
The HUTCHINSON Dictionary of SCIENCE second edition.

Before looking at the factors that can alter the rate of reaction, we must consider what happens when a reaction take place.
First of all, the particles of the reacting substances must collide with each other and, secondly, they need a certain amount of energy to break down the bonds of the particles and form new ones. This energy is called the activation energy or Ea. If a collision between particles can produce sufficient energy (i.e. if they collide fast enough and in the right direction) a reaction will take place. Not all collisions will result in a reaction.

The investigation could be done using one variable and therefore have a set of results which were related in some way. The variables that could be used are:

1. Concentration
2. Particle size/surface area
3. Pressure (for reactions involving gas)
4. Temperature
5. Light
6. Presence of a catalyst.

These variables can be used because:

1. The more concentrated the reactants, the greater the rate of reaction will be. This is because increasing the concentration of the reactants increases the number of collisions between particles and, therefore, increases the rate of reaction.

2. When one of the reactants is a solid, the reaction must take place on the surface area of the solid. By breaking up the solid into smaller pieces, the surface area is increased, giving a greater area of collisions to take place and so causing an increase in the rate of reaction.

3. When one or more of the reactants are gases an increase in pressure can lead to an increased rate of reaction. The increase in pressure forces the particles closer together. This causes more collisions and increases the rate of reaction.
4. An increase in temperature produces an increase in the rate of reaction. A rise of 10º C approximately doubles the rate of reaction. When a mixture of substances is heated, the particles move faster. This has two effects. Since the particles are moving faster they will travel greater distance in a given time and so will be involved in more collisions. Also, because the particles are moving faster a larger proportion of the collisions will exceed the activation energy and so the rate of reaction increases.

5. The rates of some reactions are increased by exposure to light. Light has a similar effect as temperature because it produces heat.
6. A catalyst is a substance, which can alter the rate of a reaction but remains chemically unchanged at the end of the reaction. Catalysts usually speed up a reaction. A catalyst, which slows down a reaction, is called a negative catalyst or inhibitor. Catalysts speed up reactions by providing an alternative pathway for the reaction, i.e. one that has much lower activation energy. More collisions will, therefore, have enough energy for this new pathway.

Extracts from: Letts Study Guide, GCSE CHEMISTRY.

All this information is relevant to my investigation, as I now know what would happen to the molecules when using different variables. It also makes it easier to decide what variable I am going to use in this circumstance.

I decided to use the concentration of acid as my variable. I used 5 different strengths of hydrochloric acid. These strengths would determine the rates of reactions. I decided to measure the acid in millilitres. I predicted that the higher the concentration of the acid, the faster the reaction between magnesium ribbon and the hydrochloric acid. This would be because there were more acid molecules to react with the magnesium ribbon. I decided that I would do 5 experiments and the different concentrations of hydrochloric acids were:

v 1.0 molar
v 1.25 molar
v 1.50 molar
v 1.75 molar
v 2.0 molar

Before doing the actual experiment I decided to do some preliminary work. These were to tell me the details that I would need to know for my investigation to be successful. I saw from these preliminary investigations that the magnesium ribbon started to react with the hydrochloric acid the moment that I dropped it in. I decided that it would be a good idea to start timing the second that I dropped it in. When the ribbon had been eaten away by the acid, it stopped fizzing. I decided that I would stop timing the second that the fizzing stopped. I discovered from my preliminary experiments that when I used a low concentration of hydrochloric acid, for instance, 0.25 molar, it took a long time for the magnesium ribbon to be eaten away. I decided that it would be impractical to spend time on the following strengths of hydrochloric acid:
v 0.25 molar
v 0.50 molar
v 0.75 molar

This was because they were the three slowest strengths of acids available to react with the magnesium ribbon over a period of time. I also learnt from my preliminary experiments that it was sometimes quite difficult to stop timing on the exact moment that the fizzing stopped. I decided therefore that I would carry out each of the 5 experiments three times and find the average time as this would result in a more accurate figure.

When the magnesium ribbon reacts with the hydrochloric acid, magnesium chloride is formed. I wrote down the equation to show this:

Magnesium + Hydrochloric acid = Magnesium Chloride + Hydrogen
Mg + 2HCl = MgCl + H

The equipment I needed for the investigation were:

v Magnesium ribbon- 15 pieces, 1cm long and weighed 0.01g
v Hydrochloric acid - 30 ml of 1.0 molar
30 ml of 1.25 molar
30 ml of 1.50 molar
30 ml of 1.75 molar
30 ml of 2.0 molar

v Test tubes - 5
v Test tube rack
v Stop clock
v Pipette
v Measuring Cylinder
v Thermometer
v Safety goggles

I decided to do 5 experiments, three times each, using all the information that I gained while I was doing my preliminary experiments.
To ensure a safe experiment and working environment I needed to have at least 1 meter squared of working space around me, wear safety goggles at all times when using acid, use a test tube rack instead of holding the test tubes, secure all equipment and make sure that all the equipment were fully functional and not damaged.
To make the experiment a fair test I used the same amount of acid for all experiments, only changing the concentrations. I used the same size of magnesium ribbon and weight (approximately 0.01g). I also started the stop clock when the magnesium touched the acid and stopped it when the magnesium stopped fizzing for each experiment. I always washed out the test tubes when an experiment had finished so the different concentration wouldn´t get mixed together causing strange results.

First I measured out the amount of hydrochloric acid using the measuring cylinder. I used a pipette to pour the acid into the measuring cylinder as to be accurate. I needed 10 ml of acid in the cylinder and poured it into a test tube. I then put a thermometer into the test tube for 1 minute to check the temperature. I did this to see if the experiments with the same strength of acids affected the rate of reaction if there was a change in temperature. I then got a piece of magnesium ribbon about 1 cm long weighing 0.01g and dropped it into the acid and started timing the moment that the magnesium ribbon touched the acid solution. When the magnesium ribbon stopped fizzing, I stopped the clock and recorded the number of seconds (rounded up to nearest second) taken for the reaction from start to finish.

I made a table to record my results in. The table is shown below.

Experiment Strength of hydrochloric acids in 10 ml No. of Mg ribbon pieces (0.01g) Test 1 secs. Temp Test 2 secs. Temp Test 3 secs. Temp AverageSecs.
1 1.0 molar 1 151.0 18 ºc 141.0 18 ºc 117.0 18.4ºc 136.3
2 1.25 molar 1 81.0 17 ºc 76.0 17.5ºc 74.0 18 ºc 77.0
3 1.50 molar 1 58.0 17.5ºc 56.0 18 ºc 56.0 18 ºc 56.3
4 1.75 molar 1 50.0 18 ºc 41.0 18º c 31.0 18 ºc 40.7
5 2.0 molar 1 20.0 19 ºc 22.0 19 ºc 16.0 21 ºc 19.3

To calculate the average time that it took for the magnesium to be eaten away by the acid, I did the following calculation:

Test 1 + Test 2 + Test 3 = Average time
3

As I already have mentioned, I used a measuring cylinder to make the measurements and used a pipette for further accuracy. I did each experiment three times so I would be able to calculate averages and thereby get more accurate results. I recorded the results in seconds instead of minutes in order to obtain more precise results. I used a stop clock instead of a 24-hour clock so I could look at the milliseconds and round it up to the nearest second, which made the results more exact.

It was noticeable, when looking at the results table, that the more concentrated acid had a faster rate of reaction than the less concentrated acid. This was probably because there are more particles in a concentrated acid and therefore more collisions will occur. For instance, 1.0 molars´ average time, 136.3 seconds, is longer than 2.0 molars´ average time, which was 19.3 seconds.

I made a graph to show the results.

The graph above supports my original prediction of: the more concentrated the acid the faster the rate of reaction because it shows the time difference between the different strengths of acids. In a higher concentration there are more acid particles to react with the magnesium ribbon and therefore it is eaten away faster.
I conclude that changing one factor does have a significant effect on the rate of reaction as we have seen.

Looking at the set of results obtained, you can clearly see that they all follow the expected pattern. This is pattern suggests that the reaction rate increase when the concentration of the acid increases because if you increase the concentration of the acid you are introducing more particles into the reaction which will in turn produce a faster reaction because there will be more collisions between the particles which is what increases the reaction rate.

The evidence I have been able to gather from this investigation seems to lead to a quite firm conclusion. I might not have been able to find the exact speed of the reactions but the pattern seems to be correct as I have repeated readings three times and as it agrees with the information I have researched.
I used the variable of concentration, which seemed to be of a good choice as it would show the results of how more acid molecules reacting with magnesium, would result in a faster reaction.

There will always be ways in which you can improve your investigations and the same thing goes to my investigation.
I found it very hard to measure out the exact number of millilitres for the acid even though I used a pipette and I was also in a hurry. If I was to redo this investigation I would put some more effort into measuring the acid. I could have used the wrong concentration of acid by accident and that would have affected the speed because there would have been fewer or more acid particles to react with the magnesium ribbon. Next time I do this experiment I would try to remember which acid I am using so it doesn´t get mixed up. Every time I washed a test tube or a measuring cylinder, I did not dry it before using it. This may have affected the rate of reaction, as water would dilute the acid. To improve my results, I could dry the test tubes and the measuring cylinder after they are washed to prevent diluted acids. The size and weight of the magnesium would have affected the rate of reaction. The experiment could be improved by measuring, adjusting and weighing the magnesium ribbons so they all are the same size and weight. I also found out from background information, that the magnesium ribbon is covered with a whitish deposit. This deposit was magnesium oxide where the magnesium had reacted with the air. I would imagine that some pieces had only a little of this oxide and some had a lot. The pieces of magnesium ribbon that did not have much oxide on them reacted faster than those with a lot. To improve my results, I could clean the magnesium oxide of all the magnesium pieces using some sandpaper, and this would mean that the acid would not have to eat through the magnesium oxide before reacting with the magnesium. In my investigation I also measured the temperature to see if there would be any change in the rate of reactions. From my results it was noticeable to look at each experiment and see how the temperature had affected the rates of reactions. For instance, if we refer back to the table on page 5 and look at experiment 5, test three is slightly faster than test 1 or test 2 because it has a temperature of 21º, where as the other two tests both have a temperature of 19º. To improve my investigation I could assure that the temperature was constant all the time. I could also do more readings to get nearer to a more accurate result.
In my investigation I used concentration as my variable. To improve my investigation further, I could use other variables such as, surface area, temperature, pressure for gas, and a presence of a catalyst.
These variables would hopefully prove that they all help speed up a chemical reaction.

Rates of reactions between HCL and magnesium ribbon.