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Does concentration affect the rate of reaction between magnesium strips and hydrochloric acid?

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Introduction

Science Coursework Does concentration affect the rate of reaction between magnesium strips and hydrochloric acid? Scientific knowledge Aim: The aim of this assignment is to find out if concentration affects the rate of reaction. I will be experimenting this with hydrochloric acid and magnesium strips. Everything is made up of particles, atoms and molecules that are continuously moving around and vibrating. In order for chemical reactions to occur, the particles in the reactants must collide with each other. Particles must have enough energy to break the bonds in the reactants in order for the reaction to take place; otherwise the particles will just bounce off each other. For a faster rate of reaction more energy is needed. More energy can be gained by increasing the temperature. This is because the higher the temperature, the more energy the particles have and therefore they vibrate and move around more. This extra energy provides the particles with more kinetic energy and the particles move around more often, therefore resulting in more successful collisions per second. To speed up a reaction the particles have to move around more often. Activation energy is the energy level that must be overcome by the reactants in a chemical reaction in order for the reaction to occur. For reactants to form products they must collide. To do this they must have enough energy to react, otherwise they just bounce off each other. In the case of magnesium and hydrochloric acid, activation energy must be reached if the reaction is to take place. If the particles in the reactants collide fast enough and in the right direction, they will produce the right amount of energy to break the bonds of the reactants and make a new product. Concentration tells us how many particles of a solute are dissolved in a solvent. The more particles there are dissolved, the more concentrated the solution. ...read more.

Middle

I will repeat this experiment three times for each acid. The ranges of hydrochloric acid I intend to use are: 0.5m 1.5m 2.5m 4m 5m To ensure a safe experiment and working environment I need to have at least one metre squared of working space around me and wear goggles at all times to protect my eyes from the harmful acid. I will tie my hair back to avoid contact with any harmful substances. I will wipe away any spillages immediately to avoid any reactions. I will make the experiment accurate by using a pipette to measure the volume of acid correctly and accurately and I will also look at the measured acid from eye level. I will measure the time in seconds so that the results are more accurate and precise. I will always wash out the measuring cylinders to prevent the acid concentration being mixed up and giving us strange results, but I will also dry the measuring cylinders to prevent cross contamination, so that the water does not dilute with the acid. I will know that my results are reliable because I will repeat this experiment three times and I should get a similar result as before because the results should follow a pattern. To make this experiment a fair test, I will weigh the magnesium strips, to ensure that I am using the same amount and length of magnesium each time. I will also use the same amount of acid for each experiment to make it fair. I will start the stopwatch as soon as the magnesium touches the acid and stop the stopwatch as soon as the magnesium has disappeared and the reaction has stopped fizzing. Before doing this experiment I did try and weigh the magnesium strips but the scale was not powerful enough to weigh it and therefore it may have given me inaccurate results. The amount of acid I will use for this experiment is 25 cm3 and the amount of hydrogen I will be collecting is 25cm3 for each experiment. ...read more.

Conclusion

Also, in this experiment it was very difficult to collect the gas as you had to hold onto the measuring cylinder in the washing up bowl during the reaction, therefore some of the gas may possibly have escaped and so the result would not be accurate. I could improve on this by using a gas syringe to collect the gas in the next experiment. In the reaction, the exothermic factor caused a rise in temperature and therefore this will have affected the results. This is because the unreacted particles will gain more energy from this extra heat and therefore will collide more often with successful, effective and frequent collisions, leading to a faster rate of reaction. I could control this temperature by doing the experiment in a water bath which includes a thermostat, which is set at a constant temperature. To see what temperature it should be set at, I would do the 5 molar acid experiment and measure the maximum temperature rate at the end of the reaction. I would set the thermostat at that temperature, this discounts the exothermic factor. I also found out from background information that the magnesium we were using was not 100% pure magnesium; it was magnesium oxide where the magnesium had reacted with the air. This may have affected the results because it may have taken longer for the acid particles to reach the magnesium itself and then react with it. To improve my results, I could clean the magnesium oxide from the magnesium by using sandpaper to sand away the oxide layer. Also, to make the results more reliable and accurate, I could weigh the magnesium strips after the oxide has been cleared. In my investigation, I used concentration as the variable, to improve my investigation further, I could concentrate on the lower ranges of acid such as 0.1, 0.2, 0.3 etc. and see how they affect the rate of reaction. I could also use other variables such as, surface area, temperature, pressure for gas and the presence of a catalyst and observe how they affect the rate of reaction. ?? ?? ?? ?? 1 ...read more.

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