Rates of ReactionBACKGROUND INFORMATIONWhat affects the rate of reaction? 1) The surface area of the magnesium.
2)The temperature of the reaction. 3) Concentration of the hydrochloric acid. 4)Presence of a catalyst. In the experiment we use hydrochloric acid which reacts with the magnesium toform magnesium chloride. The hydrogen ions give hydrochloric acid its acidicproperties, so that all solutions of hydrogen chloride and water have a sourtaste; corrode active metals, forming metal chlorides and hydrogen; turn litmusred; neutralise alkalis; and react with salts of weak acids, forming chloridesand the weak acids. Magnesium, symbol Mg, silvery white metallic element that is relativelyunreactive.
In group 2 (or IIa) of the periodic table, magnesium is one of thealkaline earth metals. The atomic number of magnesium is 12. Magnesium(s) + Hydrochloric acid(aq) = Magnesium Chloride(aq) + Hydrogen(g)Mg+2HCl= MgCl2+ H2In the reaction when the magnesium hits the acid when dropped in, it fisses andthen disappears giving of hydrogen as it fisses and it leaves behind a solutionof hydrogen chloride. The activation energy of a particle is increased with heat. The particleswhich have to have the activation energy are those particles which are moving,in the case of magnesium and hydrochloric acid, it is the hydrochloric acidparticles which have to have the activation energy because they are the onesthat are moving and bombarding the magnesium particles to produce magnesiumchloride.
The rate at which all reactions happen are different. An example of a fastreaction is an explosion, and an example of a slow reaction is rusting. In anyreaction, reactants chemical reactions products. We can measure reactions in two ways:1) Continuous:- Start the experiment and watch it happen; you can use acomputer logging system to monitor it. I.
e. Watching a colour fade orincrease. 2) Discontinuous:- Do the experiments and take readings/ samples from theexperiment at different times, then analyse the readings/samples to see how manyreactants and products are used up/ produced. Reaction rate = amount of reactant used up time takenIf the amount used up is the same each time then the only thing that changes isthe time taken. so, reaction rate 1 time taken. rate = Ktime taken.
Where K is the constant for the reaction. For particles to react:-a) They have to collide with each other. b) They need a certain amount ofenergy to break down the bonds of the particles and form new ones. This energyis called the Activation Energy or Ea.
When we increase the temperature we give the particles more energy which:1) Makes them move faster which In turn makes them collide with each other moreoften. 2) Increases the average amount of energy particles have so more particles havethe activation energyBoth of these changes make the rate of reaction go up so we see a decrease inthe amount of time taken for the reaction and an increase in time taken. = 1Time taken reflects the rate of reaction. Because temperature has an effect on both the speeds at which the particlesreact and the activation energy they have a greater effect on the rate ofreaction than other changes. A change in concentration is a change in the number of particles in a givenvolume.
If we increase the volume:-a) The particles are more crowded so they collidemore often. b) Although the average amount of energy possessed by a particle does notchange, there are more particles with each amount of energy;- more particleswith the activation energy. a) is a major effect which effects the rate, but b) is a minor effect whicheffects the rate very slightly. In this experiment we are not concerned with whether the reaction isexothermic or endothermic because we are concerned with the activation energyneeded to start and continue the reaction. PREDICTIONSI predict that as we increase the temperature the rate of reaction willincrease.
If we increase the temperature by 100C the rate of reaction will double. I predict that if we increase the concentration of the acid the reaction ratewill increase. If the concentration of the acid doubles, the rate of the reaction will alsodouble. LINKING PREDICTION TO THEORYReaction Rate and Temperature.
The collision theory describes how the rate of reaction increases as thetemperature increases. This theory states that as the temperature rises, moreenergy is given to the
