Amount Of Acid And Amount Of Calcium example essay topic

Planning Aim of experiment: The aim of this experiment is to investigate the rate of reaction of an acid with a rock. There are different factors that effect the rate of reaction between calcium carbonate (marble chips) and hydrochloric acid. The factor that concerns my investigation is the concentration of the liquid reactant, which in this case is the hydrochloric acid. The aim is to experiment and to observe how the concentration of the acid effects the rate of reaction between the limestone and the acid. Since limestone is a carbonate, a good sample of it would be marble known as calcium carbonate. There were many different type of acid's available including nitric acid, hydrochloric acid and sulphuric acid.

Hydrochloric acid was chosen to use in the experiment, as it would give us accurate results as it contained the properties of acid rain. Calcium Carbonate (marble chips or limestone) would be used as a rock. Calcium Carbonate (Marble) is a metamorphic rock. Outline of investigation: As stated in the aim of the experiment, we had to investigate the rate of reaction of an acid with a rock. There are 4 main ways in which a rate of reaction can be changed. They are listed below, .

Temperature of acid. Concentration of acid. Amount of catalyst. Surface area of calcium carbonate In this particular investigation we are going to investigate the reaction of calcium carbonate and hydrochloric acid. The word equation is as follows, Calcium Carbonate + Hydrochloric acid 'a Calcium chloride + Water + Carbon Dioxide The symbol equation is as follows, CaCo 3 (s) + 2 HCL (aq) 'a CaCl 2 (aq) + H 2 O (l) + CO 2 (g) Looking at the above, the question poised is, how do we measure the rate of reaction? Well there are many ways to measure the rate of reaction.

Firstly we need to decide whether we want to measure the reactants used up or how quickly the products are forming. If we decided to measure the reactants used up we would have to keep the amount of calcium carbonate limited, as referring to the hypothesis in this section, we realised that the reaction in the experiment would be fairly slow, hence calcium carbonate would have to kept to a minimum. However i decided that i would measure the products forming which would be the volume of gas given off. As seen from the above equation, the gas given off is carbon dioxide. To measure the amount of carbon dioxide given off, a gas syringe would be needed. Underneath is a diagram showing how it would be added to the experiment.

Above clearly shows how the rate of reaction will be measured. The variables chosen are shown in the next section below. Concentration of acid was the variable chosen to change, and if time was available we would look at the surface area of calcium carbonate as our second variable. We would then make a comparison between the concentration of acid, to find out whether it effects the rate of reaction. We would then work out the exact rate of reaction by finding out the amount of carbon dioxide / by the time taken.

This will enable us to compare the rates of reaction. Then the moles will be worked out. We would also work out exact rates of reaction at a certain time by using tangents on our graphs. Preliminary Investigation: Only one preliminary experiment was done, as I believed the experiment was fairly straightforward. 75 ml of acid would be used, with 5 different concentrations. 0.25 Molar, 0.5 Molar, 1 Molar, 1.5 Molar and 2 Molar.

This will give us a good set of accurate results, which data can be interpreted from. If surface area was the variable, only 3 different sets of data can be taken from it, as the acid would be a fixed variable. 3 sets of results are not enough to get good accurate results, as there is not enough data to support a conclusion. The preliminary test was used just to set up the whole experiment and to check if our method of collecting the carbon dioxide actually worked and everything went according to plan. We didn't record the results but we felt that the whole reaction took place well and it gave the information we need to help us with measuring the rate of reaction. We decided upon the preliminary test that 75 ml of acid would be used, as we needed to make sure that access acid was going to be used, and we were collecting the product formed and not the product being used up hence we wouldn't have to wait that long in order for the acid or for the calcium carbonate to be used up.

During the preliminary investigation, the whole experiment was set up and different aspects were checked. We realised that if we waited for the whole experiment to finish, the 0.5 Molar, predicted to be the slowest reaction, would take very long and would take about 1 hr 30 minutes to finish, hence we decided that we would let each experiment react for 30 minutes. The preliminary test also made us decide that, 1 gram of small sized surface area calcium carbonate would be used. To try and keep the surface area as close as possible, the same amount of pieces of calcium carbonate would be used, 6 Pieces of calcium carbonate would be used in each experiment in total weighing about 1 gram in total. Prediction / Hypothesis: My prediction is based upon the collision theory. I believe that if the concentration of the acid increases, the rate of reaction also increases.

Hence the fastest reaction will be the one where the acid is 2 molars. The slowest reaction will be the one where the acid is 0.5 Molar. However if the same weight of calcium carbonate and the same amount of acid is used which will be the case, the products formed will be the same hence at the end of the experiment the same amount of carbon dioxide should be obtained. Refer to the background information / theory for my hypothesis of the experiment. A predicted graph is shown below, Theory / Background Knowledge (Collision Theory): We have to look at the factors that can alter the rate of reaction (explained above), we must consider what happens when a reaction takes place.

The particles of calcium carbonate and hydrochloric acid must collide with each other and a fixed amount of energy called activation energy must be reached if the reaction is to take place. If a collision between particles can produce sufficient energy, if they collide fast enough and in the right direction a reaction will take place. Not all collision will result in a reaction (0.25 Molar especially as not enough particles + not enough energy to produce reaction) A reaction is speeded up if the number of suitable collisions is increased. (2 Molar especially as there are more particles and high amount of energy for collision to be done.) The more concentrated the reactants (hydrochloric acid), the greater will be the rate of reaction. This is because increasing the concentration of the hydrochloric acid will increase the number of collisions between particles and, therefore, increases the rate of reaction. The acid particles move randomly and as the concentration of the acid increases, there is a greater change of acid particles colliding, and reacting, with particles on the surface of the marble.

(Hence smaller surface area of the marble (same weight) will collide more, as there is more surface for the acid particles to collide with. ). Refer to the appendix for more information. Variables / Fair Testing: In order to keeps this investigation fair to produce accurate results, only 1 variable can be changed. The different variables are listed below, . Concentration of acid.

Amount of catalyst (if any). Temperature (of acid). Surface area of rock. Amount of Acid.

Weight of Calcium Carbonate. Other changes of physical equipment (e.g. beaker) Explain all the above variables. Above are the different variables that could be changed. In order to make this a fair test, only 1 variable can be changed.

The variable that i am going to change is the concentration of the acid. The concentration of the acid will effect the rate of reaction. And in order to keep this a fair test, all other variables must be kept constant. If time was available surface area would also be investigated.

However first preference would be to investigate the concentration of the acid. All the others in the list of variables will have to be kept constant. Amount of acid and amount of calcium carbonate chips will have to be kept constant. The amount of acid will have to be 75 ml to ensure it is excess acid whilst the amount of calcium carbonate chips will have to be 6 for the small surface area and the total would have to be 1 gram as that is a constant value. For large surface area calcium carbonate chips (if time) there would have to be 3 pieces which would equal 1 gram to ensure that a comparison could be made. Fixed Variables which will be kept constant: - the temperature, which will be kept at room temperature, a thermometry will be placed into the acid each time before repeating a new test - The mass of Calcium Carbonate will be 1 gram at all times and will be weighed using the SAME measuring scales at all times, as the measuring scales may have a bit of inaccuracy e.g. 0.01 g, hence same scales.

For small sized marble chips, 6 of them will be used (to try and keep the surface area relatively the same, however this is difficult as each piece has a rough area which makes it difficult to calculate the surface area, hence this will be a variable which really cannot change. Hopefully it will not effect our results too much. The same amount of Hydrochloric Acid will be used which will be 75 ml. This will ensure a fair test as the acid has to be excess all the time otherwise the experiment may finish before the calcium carbonate has reacted with all the acid. - The same equipment will be used in all experiment including the gas syringe as some gas syringes get pushed by different amount of pressures, hence it is important that the same amount of pressure gets pushed at all the time. - Time intervals will be changed depending on the concentration of the acid being used, as for example have 30 seconds interval for 2 Molar acid will give us inaccurate results as the range is too big.

So depending on the Molar of the acid different scales will be used. Each experiment will be timed for 30 minutes maximum as i believe sufficient results will be obtained by then. To promote a fair test we will have to make sure we control all the other variables and only change the variable of concentration every single time. To do this, we are going to keep the temperature at room temperature and keep all the materials around the same area so they aren't exposed to excessive heat etc. We will also make sure we have a fixed weight of marble to keep the test fair.

To make sure that our results are reliable and accurate, we are planning to repeat our experiments more than once; we will repeat each experiment twice and if time is available; we will try to repeat a third time. We will then produce an average of results that will prevent us from giving flawed results. Measurements will be recorded to a suitable degree of accuracy. For example, time will be recorded to the nearest 1 second and I will show the possible errors on our graphs. In dilute acid there are less acid particles. This means there is less chance of an acid particle hitting a magnesium particle as compared with acid of a higher concentration.

In concentrated acid there are more acid particles, therefore there is a greater chance of an acid particle hitting a magnesium particle. The more successful collisions there are the faster the reaction. By doing all the above, i should be able to collect accurate and reliable data. Method / Task/Precautions & Step by Step Instructions - equipment used (Diagram) Techniques & Safety / Measurements: Safety in the experiment is aspect in this experiment as we are working with acid. Acid is corrosive and dangerous hence safety goggles have to be used at all times to ensure safety of the experiment. Acid must be treated with care and if spilled should be cleaned quickly.

However safety in the lab is a key factor for also ensuring the results obtained were accurate There were 5 main measurements to be taken 0.25 Molar acid, 0.5 Molar acid, 1 Molar acid, 1.5 Molar acid and 2 Molar acid. If time were available all the above 5 measurements would be done twice, once with small sized calcium carbonate surface area chips which will weigh 1 gram in total (6 pieces will be used). 6 pieces will have to be used in all 5 experiments as we have to try and keep the experiment as fair as possible. Even though the surface area will not be exact, the surface area will be as close as possible and this will be a topic of fair testing. This cannot by no means, be a 100% fair test because the surface area cannot be kept constant as the shape of the marbles are rough hence making it difficult to calculate surface area.

However we can make sure that the same amount of pieces are used and a same total weight of 1 gram can be achieved by rubbing the marble against a rough edge to extract powder to make it lighter. If time was available we would repeat the above method, for large surface area calcium carbonate chips. This would be a second variable and would tell us whether or no surface area effected the rate of reaction. However out first preference was the concentration. We would not repeat the results, as i believed the experiment was very time consuming, and i believed that a second variable would be more valuable then repeating. Also i believed that the experiment was fairly straightforward, hence not requiring repeating, as long as all measurements was correct.

75 ml of acid would be used and the gas syringe would have to be properly working i.e. it moved up and down freely. Great time was given whilst measuring out our marble chips and acid to ensure very good accuracy, otherwise the experiment would go a mess. As for the large surface area marbles, 3 of them would be used at a time, with a total mass of 1 gram. Method: 1 gram will be used because, the gas syringe can only collect gas up ill 100 ml (cm cubed). Aim is to do 10 experiment large 3 pieces, small 6 pieces 1 gram...

30 minutes some experiments finished some nowt. Chips were inaccurate, as surface area., all roughly same size. The range of results will change as shown in preliminary experiments. Powder will be taken off to make exactly 1 g: Analysis and Conclusion Referring to the results and tables and graphs drawn, it is obvious that when the concentration of acid increases the rate of reaction increases.

As more time was available, the surface area was also investigated, and the conclusion from this was that the larger surface area (more + smaller pieces). This is based upon the collision theory. The rates of reaction depend mainly on the number of collisions between the particles in a given unit of time. In this particular investigation we investigated the reaction of calcium carbonate and hydrochloric acid. The word equation is as follows, Calcium Carbonate + Hydrochloric acid 'a Calcium chloride + Water + Carbon Dioxide The symbol equation is as follows, CaCo 3 (s) + 2 HCL (aq) 'a CaCl 2 (aq) + H 2 O (l) + CO 2 (g) For the experiment we measured the about of carbon dioxide released in the experiment, and we found out as the concentration of acid increased, shorter time was needed for the same amount of carbon dioxide to be released.

The same amount of carbon dioxide was released in all experiments because, the amount of acid used was constant, as excess acid was used, hence all the calcium carbonate was able to react, and since the mass (g) was always constant, the same amount of carbon dioxide was released in all 10 experiments. In order for the calcium carbonate to react with the hydrochloric acid, 1) They must collide with each other 2) The collision must have sufficient energy Using A as 1 particle of calcium carbonate and B as 1 particle of Hydrochloric acid this can be explained, 0.25 molar of hydrochloric acid A + B + B (2 B's as balanced equation shows, 2 particles of hydrochloric acid is needed to react with one particle of calcium carbonate.) Hence 2 different collisions, however collision energy is low as only 0.25 molar, too many water molecules present. Only 2 possible combinations of collision.