Investigating How Different Concentrations Affect the Rate of Reaction

Investigating How Different Concentrations Affect the Rate of Reaction
In this investigation I am investigating the effect of one factor on the rate at which calcium carbonate reacts with hydrochloric acid. I have decided to change the concentration of the acid to investigate how different concentrations affect the rate of reaction, and to discover what amount, at which concentration releases a higher quantity of gas. There are other factors, which could have been used as the variables. My method is as follows I will measure out 2 grams of marble chips using the scales, and add them into a conical flask and 20ml of hydrochloric acid into a measuring cylinder. I then added the acid into the conical flask with the marble chips and started the clock straight away. After time periods of every 30 seconds I measured the amount of gas in the syringe, this will continue until one of two things happened. Either the volume of the gas syringe gets past 100cm and it is necessary for the back of the gas syringe to be taken out, otherwise it could drop out and smash, or the volume of gas remains constant for 1 minute, and then that particular experiment will end. 1Molar Room temperature-27 c. 1M Room temperature-27?c. Time Time Experiment 1 -????- (Large chips) Experiment 2 (Small chips) Experiment 1 (Large chips) Experiment 2 (Small chips) Experiment 3 (Small chips) Experiment 3 (Small chips) 0 0 0 0 20 21 6 21 40 49 17 43 60 73 28 59.5 80 93 38 71.5 100 47 79.5 120 54 85.5 140 60 89.5 160 65 91.5 180 68 92 200 70.5 92.5 220 72.5 92.5 240 74 92.5 260 74.5 280 75 300 75 320 75 Average time= 213.33333 We used this experiment as our preliminary experiment, and from this I concluded that after doing experiment 1, large chips were not appropriate for this experiment.
This is because the experiment did not last very long, because the gas was being produced so quickly, and therefore the end of the gas syringe had to be taken off. We thought that if the experiment lasted slightly longer it might make the results more reliable, as well as being easier to understand and to compare. Because of this I carried on throughout the rest of the experiments using small chips. From doing the preliminary experiment I worked out the average, so I had a rough idea of the length of time the experiments would take. After each experiment I will throw away all of the used marble chips because the reactant has been used up. To get the best possible results I am going to test each of the experiment 3 separate times to enable me to judge the amounts of gas produced fairly and decide if they are correct, but also to make it more reliable. As with any investigations great care should be taken and the experiment should be undertaken in a sensible manner. I will wear safety goggles throughout the investigation. I will be careful so as not to spill any acid, but would ensure there was nothing near the experiment that could cause an accident or be damaged if an accident did occur. In this experiment I will have to make sure I am careful with all glassware in case it breaks and if it does to make sure it is immediately cleaned up. As I will be using a conical flask its wide bottom gives a more secure base. Also, I must be careful especially with the stronger morality acid because it will be corrosive so I must make sure I do not spill it on my hands or in my eyes. I will have to check the apparatus for any broken pieces, that way, I can avoid injury to myself, or avoid a mistake in my experiment through a leak. After checking that everything is safe, I will do the experiment. I will try to make it as reliable as possible by taking the most accurate measurements at the most precise times. I will also make sure that the mass of Calcium Carbonate is precise and that in all the experiments done it is the same, or at least very close. I will also make sure that there is the same amount of Hydrochloric Acid in each experiment. If I do this I think my Hypothesis will be accurate. I will also make the experiments more reliable by repeating each experiment 3 times, and getting an average. To ensure a fair test I must also make sure that the flask is not disturbed, as any movement of the flask will result in more collisions taking place between the acid and Calcium Carbonate, thus speeding up the reaction. I must replace the marble chips each time the method is restarted as during the reaction the marble chips are being constantly eaten away, this means that the grain size is being reduced. If the surface area of the grains is larger/smaller then there will be less/more molecules available for collision, thus the amount of successful collisions is affected, therefore the rate of reaction will be different. I was careful to make this a fair test by keeping all the variables (apart from concentration) constant. Also we must try and have the syringe in the same position each time so no different forces are acting on it, affecting the results, each time, we have to keep it dry as well because it sticks when it gets wet. We will do the experiment in room temperature. The temperature has to constant as if the acid got hotter then the heat energy would turn into kinetic energy in the particles causing them to mover faster and collide with the marble chips more often, speeding up the rate of reaction. Equipment, which will be needed, includes a stand, which will hold the gas syringe. The Hydrochloric acid (HCl) reacts with the chips and gives of gas (CO2), which is collected in a gas syringe. This device is held with a clamp attached to a stand. Using the graduated gas syringe we were able to get precise readings of how much gas is being given off. The syringe n needs to be intact with no leaks. The results, which will be collected, will then be put in to a rough chart. Other equipment needed consist of a rubber tube attached to the cork to fasten the gas syringe to the test tube. The test tube I use needs to be clean to avoid any other chemicals interfering with my experiment. I need an accurate timer as I will be taking down results every 20 seconds, which will be done my reading off the amount of gas in the gas syringe, and recording it into a table. There are many factors that will affect the rates of reactions. Firstly, the surface area of the marble chips affects it, as the size will determine the rate of reaction. Chemical reactions are interactions that are often affected by physical conditions. One of these physical conditions is the amount of exposed surface area. In order for a chemical reaction to occur, molecules of different substances must collide with each other. If the substance is broken up into pieces rather than being in one piece, more surface area is exposed. This diagram below shows this: The amount of hydrochloric acid can affect the rate of reaction because the more acid there is compared to the chips, the faster the reaction will occur. If there was a smaller amount of acid compared to the chips, there would be a smaller amount of acid to each calcium carbonate chip, and therefore the reaction would be slower as less percentage of the acid id there to cover less surface area of the calcium carbonate. The amount of hydrochloric acid, which I have chosen to use, is 20ml. Temperature is also a factor which could be changed as the reactions gets its energy from heat, and temperature it is working at, it is the heat which gives the reaction energy. When heat is applied the particles begin to collide, as the amount of energy is increasing, die to the increase in temperature. Because of this higher level of energy the more collisions between the particles there are compared to if the temperature id low, and there would be less energy given to the particles, and therefore fewer collisions per second. But for my experiments I will keep the temperature at approximately 25?c which is room temperature. All of these factors are staying constant, and the temperature, mass and surface area will remain the same in all of the experiments. I think the temperature of the room could possibly affect the results, as room temperature is being used, but I cannot always guarantee that the temperature is going to remain the same. The one factor, which I will vary, is the concentration of the hydrochloric acid. An increase in concentration produces more collisions. The chance of an effective collision goes up with the increase in concentration. If the acid is diluted with water it would make it weaker and also slower to react with the chips of calcium carbonate and because there are less particles of the reactant between the water molecules, which would have enabled it to make more collisions and therefore react quicker. Whereas, if the solution has a stronger concentration with less water it would react at a faster rate, this is because there would be more of the particles reacting and colliding at a faster rate than a solution with a weaker concentration and larger surface area. The following equipment will be needed: ? Gas syringe ? Conical flask ? Measuring cylinder ? Stand ? Clamp ? Stop clock ? Calcium carbonate (marble chips) ? Hydrochloric acid (20ml) ? Scales ? Goggles Here is an image of the equipment I predict that the stronger the concentration of Hydrochloric Acid the more gas produced, by a faster rate of reaction. I think this will happen because a reaction goes faster when the concentration of a reactant is increased. The rate of a reaction depends on how many successful collisions there are between the two components, in this case being Hydrochloric acid and calcium carbonate. This is a simple law of chemistry involving the rate of a reaction, and it will be very useful for my experiment. In a diluted concentration of hydrochloric acid the chance of an acid particle hitting a calcium carbonate particle is less. But if a more concentrated solution is used there are more particles and there is a greater chance of the particle colliding with another calcium carbonate particle. [image] 0 0 0 0 20 2 1.5 2.5 40 2 1.5 2.5 60 2 1.5 2.5 [image] Chemistry Investigation By Zoe Gardner 10.1 From my graphs its is clear to see that my prediction was correct. The solution which had more molars and was therefore more concentrated had a much faster reaction. This was clear to see whilst doing the reaction in class. We only measured the amount of gas given off till we reached 100cm , and it is clear to see that the molar solution that took the longest to get to 100cm was the 0.4M solution. This would be because there are not as many acid particles as there are in the 2M solution. This mean that although particles may be hitting the marble it may not be an acid particle. Only the acid particles would react with the marble chips to form a reaction. The 2M solution reacted so fast that it reached over 100cm of gas within 30seconds. This is a very fast reaction as there are many acid particles colliding with the marble chips.

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