Temperature By 10 The Rate Of Reaction example essay topic

TITTLE; Effect of temperature on the rate of reaction Aim I plan to investigate the effect of temperature of acid, in the reaction between concentrated hydrochloric acid and magnesium ribbon. The rate of 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, e.g. a reaction after a fire work is set. In this investigation I will test different temperatures of acid reacting with magnesium. Prediction My prediction is that as the temperature of hydrochloric acid increases, the time taken for the magnesium to disappear decreases.

I predict that when the temperature of the acid increases by 10 the rate of reaction doubles. Linking prediction to theory; Reaction rate and temperature 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 temperature of HCl increases. As the reaction continues, the temperature 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 temperature 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.

INTRODUCTION In the reaction between HCl and Mg ribbon, the HCl will dissolve the Mg and produce hydrogen gas. All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products. In this case the reactants are HCl and Mg to produce H 2 Equation of the reaction is; 2 HCl + Mg = H 2 + MgCl 2 Background theory states that all substances are made up of particles, atoms, molecules or ions. Before a chemical reaction, the particles of the reactants must crush together with enough energy to break or form new bonds between the other particles.

This is known as the collision theory and it's used to predict the rate of a reaction. When chemical reactions occur, their speed is measured either by how quickly the reactants are used up or how quickly the new products are forming. Evidence to show that a chemical reaction has taken place and I could use this to record my experiment; Volume of gas given off Using the gas syringe to collect the gas that will evolve from my experiment I could use these results to calculate the initial rate of reaction. Change in mass I could put the conical flask with chosen volumes of HCl and the drop a piece of Mg ribbon into the flask then measure the decrease in weight at chosen intervals. Time taken for the Mg to dissolve Reactions take place over time; explosive reactions are really fast, while rusting is slow and a reaction between a metal and an acid is of a moderate speed. The speed of a reaction is inversely proportional to the time taken for the reaction to finish.

Different factors influence the speed of a given reaction hence could affect the reaction of my experiment, these include; Concentration of acid This could affect the rate of reaction because the higher the concentration of the acid the more acid particles per 100 cm 3 so more collisions per second and then there will be more successful collisions per second. Temperature of the acid If the starting temperature of the acid is different each time the speed at which the acid particles collide with the Mg ribbon will increase more the higher the temperature goes. This means the acid particles move with more energy. Surface area When one or more of the reactants is a solid, the more finely powdered (divided) the solid, the greater the rate of a reaction. This is because reactions occur on the surface of the solids.

If the Mg has a bigger surface area each time the experiment is done then the acid particles will have a bigger area to collide with so more collisions will occur every second. Catalyst A catalyst is a substance that increases the rate of a chemical reaction by lowering the activation energy. The catalyst remains chemically un changed at the end of the reaction. Many catalysts work by providing a surface on which other molecules or atoms can react.

They can be re- used. However my aim is to see that if I change the temperature of HCl for each experiment I will see an increase or a decrease in the rate of reaction between hydrochloric acid and magnesium ribbon. Plan Iam intending to react a chosen length of magnesium ribbon with a chosen volume of hydrochloric acid. I will measure the rate of reaction by collecting the hydrogen gas that is produced in a gas syringe that will be connected via a piece of rubber tubing and a bung to the conical flask that the reaction will take place.

I will quickly drop the length of Mg into the flask and connect the rubber tubing to it. I will then start the stop clock and record the volume of gas evolved. Apparatus Measuring cylinder (50 ml) Conical flask (50 ml) Beaker (50 ml 0 Gas syringe (50 ml) Heat proof mat Bunsen burner Tripod stand Water bath Wire gauze Thermometer Magnesium ribbon of 0.04 g (4 cm long) 2 M conc. HCl acid (50 ml) Stop watch Weighing scale Safety The things that I need to do to keep my experiment a safe one for my self and other students around me are as follows; o Wear safety goggles o Wear lab coat to protect my clothes o Safe disposal of reagents o Care in using glassware o Safe disposal of reagents Pilot study The preliminary work that I will be conducting is to find out the best mass of Mg ribbon and the best volume of HCL to use. Am going to do this by carrying out a number of calculations below; Using the equation of reaction; 2 HCL (l) + Mg (s) = H 2 (g) + MCL (S) I have chosen 0.04 g of Mg ribbon (found to be 4 cm long).

Because when using the RMM of Mg which is 24, the moles of Mg can be worked out as follows; since n = m Ar There for n = 0.04 24 n = 1.67 Hence 1 mole of magnesium = 1 mol (H 2) gas 1.67 = 24 Method o Put on safety goggles and lab coat o Collect all the apparatus to your nearest working point o Set up the apparatus as below o Using the measuring cylinder measure 50 cm 3 of the acid o Put it into the beaker and then use thermometer to measure off the 1st temperature of the acid. It should be the room temp o Put the acid into the conical flask o Then place 0.04 g of Mg ribbon into the flask and quickly cover the flask so that no gas escape o Immediately start the stop clock o At the end of reaction measure off the amount of gas produced o Repeat the above procedure using different temperatures in intervals of 10. o Use the Bunsen burner to heat the acid in order to attain the required temperatures It is important that only temperature is changed 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; o Concentration of the acid o Volume of the acid o Surface area of Mg o Length of magnesium ribbon This enables me to achieve the best possible results since accuracy is vital Table of results HCL Length of Mg temperature Volume of gas Time taken (seconds) 50 ML 0.04 19 30 45 50 ML 0.04 29 22 30 50 ML 0.04 39 16 15 50 ML 0.04 49 12 10 50 ML 0.04 59 10 8 50 ML 0.04 69 8 4 The above results are plotted on graph paper Conclusion My results in table and graph show me that if you increase the temperature the rate of reaction increases. This is because when Mg and HCl molecules collide and the reaction takes place, new bonds are formed and old ones broken. This necessitates the formation of an un stable, high energy, intermediate state in which some bonds are half formed and others half broken. The molecules must have sufficient energy to over come this un stable state before H 2 is formed.

Hence increasing the temperature of a reaction increases the number of molecules with sufficient energy to over come this so called transition state. The graph gives us a good device to prove that increase in temperature increases the rate of reaction. The graph of 1/time had the form of an's curve and it did have some relationship with the other graph. However I also stated in my prediction that if I increase the temperature by 10 the rate of reaction doubles and as you can see from the table and graph it approximately doubles hence I conclude that if you increase the temperature by 10 the rate of reaction doubles. Evaluation Was I precise in my measurements? I feel that I wasn't precise and accurate in my measurements.

Although I measured the right volumes of reactants to use I collected less hydrogen than expected this was mainly because I let some of it escape especially in the last four experiments. To get the expected results I should have acted fast by covering quickly the mouth of the flask in order for the gas to be collected and not escape. I only carried the experiment once; I should have done it more than that in order to get better results because the more experiments performed the more accuracy and skill a student acquires. And also I took long to start the stop clock it could have been more accurate if I had reacted faster than that.