1 0 M Of Acid example essay topic

Science Investigation Investigation: I have performed an experiment in order to see the effects of varying the concentration of reactants on the reaction between hydrochloric acid and marble chips. Planning: The experiment I have performed involved the reaction between hydrochloric acid and calcium carbonate (marble chips) to produce calcium chloride, water and carbon dioxide. The chemical equation for this reaction is: CaCO 3 + 2 HCl CaCl 2 + H 2 O + CO 2 Background Information: In order for a reaction to occur particles of the reactants must collide with a certain minimal energy in order for products to be produced. This minimum energy must be supplied in order to break the bonds in the reactants and allow new bonds to be formed. There are a number of variables that will affect the rate of a reaction.

In order to create a fair investigation these variables must be examined and controlled so that accurate results can be obtained and conclusions drawn. i) Temperature-Increasing temperature increases the kinetic energy of the particles. This means that collisions between reactant particles becomes more frequent and occurs with more energy. Since a greater proportion of the particles have sufficient energy to break the bonds in the reactants, more products can be formed increasing the rate of reaction. In this investigation, temperature will be kept constant at room temperature so that only the effect of concentration is being measured. ii) Catalysts-Catalysts increase the rate of reaction by providing an alternative pathway for the reaction to proceed that requires less energy and therefore takes place more quickly. In this investigation, a catalyst will not be used since the reaction should take place sufficiently quickly for accurate measurement to be taken.) Surface Area-An increased surface area increases the number of collisions between the reactants. This increases the number of collisions likely to be successful and therefore increases the rate of reaction.

In this investigation the size of marble chips (used as a source of calcium carbonate) will be kept as constant as possible so that only the effect of varying concentration is being measured. iv) Concentration-Increasing the concentration of reactants increases the number of particles available for collisions and therefore the number of particles that can be converted in to products, increasing the rate of reaction. Apparatus list: Marble chips (Calcium carbonate) Stop-clock Connection tube Retort stand Digital scales Boss and clamp Conical Flask Safety goggles Paper towels Mat Gas cylinder Rubber bung Hydrochloric acid Measuring cylinder Method: I first set up the apparatus as shown in the diagram below. I used digital scales to weigh 6 sets of 15 medium chips individually at 3.0 grams and separated them into different beakers. Then, using a measuring cylinder, I measured out 0.5, 1.0, 1.5 and 2.0 M of hydrochloric acid from the containers and into separate beakers. I then collected the retort stand, boss and clamp and set them up in the correct position. I collected a mat and conical flask, placing the flask on the mat in front of the stand.

I then collected a gas syringe and fixed it into the clamp by tightening it at the middle of the syringe. I collected a rubber bung and fixed the connection tube that comes with the gas syringe all the way through I took the first set of 15 marble chips and tipped them into the conical flask. I took the first beaker of (0.5 M) hydrochloric acid, and poured the contents into the conical flask, and then quickly fixed the connected bung into the top of the flask, simultaneously starting the stop-clock. Then, every 10 seconds I took a reading from the gas syringe of how much gas had been produced. I continued for 3 minutes (180 seconds) or until the gas syringe has reached the maximum volume, recording each result onto paper. I disconnected the bung from the conical flask and then I reset the gas syringe to 0.

I emptied the contents of the conical flask into a container and rinsed the flask with water, drying it thoroughly with paper towels. I placed the flask on the mat and repeated the procedure until all the tests were complete. To remain safe while performing the different tests, I wore safety goggles and an apron when using the hydrochloric acid. I also ensured careful handling in all parts of testing. To keep the experiment fair throughout, I needed to ensure the key variables remained constant throughout my experiment. This ensured my chosen variable of concentration was isolated in the experiment; the results are then more accurate and direct.

For temperature, I realised that in washing the conical flasks using tap water, the temperature of the flasks would vary greatly. The first flask would not be washed, meaning it would not cool significantly like the other flasks. As there were not enough flasks to use a new one after each test, I washed the first conical flask and tried to get each conical flask to the same dryness level, using paper towels. Another heat variable comes from moving the conical flasks, prior to each test; the heat from my hands transfers to the flasks.

To minimise this I handled the conical flasks from the top. This means there is no heat near the bottom of the flask, where the reaction takes place to affect it. For the key variable of catalysts, I ensured there would be no necessary interference to the results by not using a catalyst in any part of my experiment. For surface area, this applies to the marble chips. I decided there were two factors, the number of chips, and the weight of the chips. This only applies when the chips are roughly the same size, and means the surface area will be as even as possible and there is the same amount of each chip, i.e. density.

To do this, for each experiment we used 15 medium sized chips and weighed each set to be 3.0 grams, using the sensitive digital scales for the greatest accuracy. To be able to see the changes in each reaction clearly and compare results, I tested 4 different moles of hydrochloric acid, 0.5, 1.0, 1.5, 2.0. To ensure the greatest degree of accuracy I tested each mole twice, and then for plotting the results, I took the average for each point. (Time against volume produced) I also chose to take a third test if the two sets of results for one mole were significantly different, indicating an unfair part to the test. I also chose to only time for 3 minutes as this would be the maximum length of time I could allow due to the time available and number of tests needing to be performed. This also gave me enough results in order to see patterns in the graphs and compare more accurately.

Other variables I was aware of and accounted for were: Any product gas escaping between adding the hydrochloric acid to the marble chips and fitting the bung in the conical flask. I minimised this by adding the acid at a steady flow each time, and putting the bung in as soon as all the acid had been poured in. Shaking the flask to speed up the reaction. As I would not be able to ensure the level of shaking or heat increase and what the individual effect on each reaction would be, I decided that for all the tests I would leave the flask untouched while the reaction took place.

Resetting and checking the apparatus. This included making sure the gas cylinder was reset fully after each test, and that the apparatus was sealed properly prior to testing. Predictions: From the above and past scientific knowledge, i.e. a preliminary experiment, I predict that the higher the concentration of acid, the faster the rate of reaction. This is due to the concentration of reactants being proportional to the rate of reaction.

This knowledge can be demonstrated by this example: If there are 100 particles of both reactants, A and B. There is a certain chance of collisions that could then be successful. If the particles of each reactant are doubled, the chance of collisions is doubled. Therefore the rate of reaction is doubled. It is for these reasons that I predict that as concentration increases, so does the rate of reaction. Prediction graph: Rate of Reaction Concentration I can also calculate the gas produced by the reaction: Moles = Mass (g) M = 3.0 100 = 0.03 moles of CaCO 3 1 mole of CaCO 3 produces 1 mole CO 2 Therefore 0.03 moles of CaCO 3 produce 0.03 moles of CO 2 1 mole occupies 24 dm 0.03 moles = 0.03 X 24 = 0.72 dm = 720 cm Preliminary Experiment: To find out whether my method would be the most suitable to receive accurate results I chose to perform a preliminary experiment. Graph A shows the results for my preliminary experiment and indicates the line of best fit and a straight average trend line.

From my results I could see that as time increased, so did the gas being produced, indicating that the reaction was taking place successful. Obtaining Evidence As I have previously mentioned, certain precautions were taken and ensured throughout testing to certify safety. After recording the results, I needed to be able to see, and thus understand them clearly in order to make graphs correctly and accurately. In the first instant that the two reactants made contact, I observed nothing occur. However once the acid had settled inside the flask a second later fizzing began to occur, producing bubbles that rose to the surface in a whitish mix, after travelling upward through the acid while some bubbles that formed, stayed on the marble chips for longer. As this bubbling occurred, there was an audible fizzing sound I detected directly from where the reaction was occurring.

I did not observe a colour change different to the marble chips, nor did I notice a visible gas rising through the already present air in the flask. Graph B shows the lines of best fit for the four different concentrations of Hydrochloric acid. Graph C shows the straight trend lines for the four different concentrations of Hydrochloric acid. Rates of reactions: To find out whether my predictions are correct, I need to directly compare the concentration of Hydrochloric acid with the rates of reaction on a graph. From this I can then make a straight trend line that will clearly show me what the trend in my results are. 0 = 90 100 = 0.9 Graph D shows the trend line for concentration of Hydrochloric acid against the rates of reaction.

Analysing: From looking at graph B, I can see my results by looking at the line of best fit. As time increases so does the volume of gas produced. For all the moles of acid this increase starts gradually before then building up to create a steeper part of the curve. For 1.0 M of acid, I can also see this curve begin to fall towards the horizontal indicating that the gas produced is now decreasing. As for Moles 1.5 and 2.0 of acid, I can see the same pattern where the curve is steepest at about half way through the test (90s).

I expect that if the time were increased for these two tests, I would see the same drop toward the horizontal. For 0.5 M of acid, the entire pattern is there, but as the results are only deviated a little it is difficult to see clearly. From looking at graph C, I can clearly see how different the results are from each other as it shows a straight trend line for each M of acid. The greatest difference can be seen between 0.5 and 1.0 M, the second largest was between 1.0 and 1.5 and the smallest difference was between 1.5 and 2.0 M of acid. I can also see that there is a pattern at the start of each test.

Graph E shows the graph for 1.0 M of Hydrochloric acid. In Graph E I have chosen to use a line of best fit as I can see how some points are not in sync with it. I have also chosen to use 1.0 M of acid to demonstrate a pattern, as it is most prominent in these results. I noticed that for each set of results, the first point on each line was above the lines of best fit as indicated. I realised that this was occurring when I placed the bung in the conical flask. As I did this, the air inside the conical flask would of compressed thus pushing air through the connection tube into the gas syringe.

The amount of increase in the syringe would then be varied as the amount the bung was pushed in. From looking at graph D I can see how concentration affects the rate of reaction directly by use of a straight trend line. It is clearly obvious that the rate of reaction is directly proportional to concentration. Predictions: As I predicted in a statement and a graph, the rate of reaction is directly proportional to the concentration.

This is seen from graph D, where each point for concentration is higher for the rate of reaction than the previous. Again indicated by the straight trend line that shows positive correlation. Conclusion: My prediction is correct because the concentration of reactants is a critical factor that affects the rate of a reaction. This can be explained by understanding how reactions occur and how different factors affect them. For reactions to occur, particles must collide with a sufficient force.

The concentration of a reactant determines how many particles of that particular reactant will be in a solution. If you increase the concentration, thus increasing the number of reactant particles, then collisions are more likely to occur. This can be demonstrated clearly by the diagram below: If you increase the number of collisions between the particles of reactants, you will consequently increase the rate of reaction. I can also demonstrate this by my rate of reaction results: 1.0 M is half of 2.0 M of Hydrochloric acid So the rate of reaction for 1.0 M should be half the rate of reaction for 2.0 M of Hydrochloric acid 1.0 M = 0.4832. 0 M = 0.9 As you can see, the rate of reaction is near to doubled, from 1.0 M to 2.0 M Evaluation: For this investigation, I found repeated results were similar to the first, indicating a good method with no substantial mistakes. I also found my results to be similar to some other peoples, while exceeding the standard of others.

To have fair results in this investigation I needed to ensure several factors remained constant throughout testing. However I can only attain a level of accuracy depending on how fair my testing is. I feel, for the equipment and materials we were allowed to use, I achieved a high standard of accuracy that gave me excellent results with minimal anomalies. Here I will list the factors that may be the cause for slight inaccuracies in my experiment. This will show how anomalies can be accounted for: . Scales not correctly read or set, giving different measurements of calcium carbonate...

Variations in pouring Hydrochloric acid, more or less agitation of the marble chips, varying surface area... Arrangement of chips when placed in flask, varying surface area for acid... Friction in the gas syringe moving at a minimal pressure, i.e. not smoothly... Displacement of gas when inserting bung into flask... Calcium carbonate dust that is weighed and then not used in the reaction... Marble chips not of equal surface area...

Differences in water left from washing the conical flask after each test. The only way a completely fair test could occur with the most accurate results, would be to follow the following factors and to account for the previous ones. SS A completely sterile and constant laboratory environment. SS Exact Hydrochloric acid volumes or larger quantities of acid and marble chips i.e. 500 ml of acid and 10 grams of calcium carbonate thus reducing surface area as a factor. SS Exact chip number, weight and surface area. SS Pure Calcium Carbonate.

SS Allow all of the reaction to occur irrespective of time. SS Take an infinite number of tests and average exactly. §.