Set up and investigate - Sample Essay
We are investigating the amount of hydrogen gas produced when using different concentrations of hydrochloric acid with magnesium. Prediction: I hypothesize that the higher the concentration of acid that I use, the less time the reaction would take which would result in a higher rate of reaction. The solvent and solute will completely react and produce the product hydrogen much quicker. Planning: We are investigating the rate of reaction between magnesium and hydrochloric acid, how it can be affected if factors were changed and the amount of hydrogen gas given off as one of the final products.
We could change the temperature surrounding the experiment in order to change the results that we acquire, the concentration of the acid that we are using, the surface area of the metal and also its shape and finally the use of a catalyst. I have chosen to use the level of concentration as it is not as difficult as the others to set up and investigate. We could measure the volume of gas given after the acid and metal have reacted, the time taken for the metal, in our case magnesium, to disappear or the change in temperature towards the end of the experiment, for instance is it an endothermic or exothermic reaction.
Like I said before we will change the concentration of the hydrochloric acid. We will measure the volume of gas given off as a final product. Our question is what we will keep the same. We will keep the same, the temperature, the use of a catalyst to any of the experiments and the surface area of the magnesium ribbon and what shape it is when subjected to the acid. The gas will be measured in cm3 and the size of the magnesium will be 5cm. Scientific explanation: Magnesium+hydrochloric acid i?? Magnesium chloride+hydrogen Mg (s) + 2HCL (aq) i?? MgCl2 (aq) + H2 (g)
In order for the magnesium and acid particles to react together: They must collide with each othe The collision must have enough energy This is basically the collision theory: 1. The particles in the liquid move around continually. Here and acid particle is about to collide with a magnesium atom. 2. If the collision has enough energy, a reaction will take place. Magnesium chloride and hydrogen are formed. 3. If the collision does not have enough energy, no reaction occurs. The acid particles bounce away again. Rate of reaction, can be changed/effected by different variables.
These are concentration, temperature, surface are or the use of a catalyst. 1. Concentration. Dilute acid, does not have many particles. This means there is not much chance of a collision occurring. When the acid is of a higher concentration, there are more acid particles. More chance of a successful collision. 2. Temperature. At low temperature, particles don’t have much energy. How ever, when heated, particles have more energy, this lets them be faster and collide more often. They also have more energy to use when they collide. Therefore there are more successful collisions. The rate of reaction increases. 3. Surface area.
The acid particles can only collide with the exposed magnesium atoms that are in the outer layer of the ribbon when a big piece of ribbon is used. When it is powdered, more atoms are exposed. Small particle have a large surface area in relation to their volume. So there is a greater chance of an acid particle colliding with a metal atom, thus the greater the chance of more successful collisions. 4. Some reactions can be speeded up by adding a catalyst. In the presence of a catalyst, a collision needs less energy to be successful. The result is that more collision can be successful and thus the greater the rate of reaction.
They also give a surface for the molecules to attach to , thereby increasing their chances of bumping into each other. Method: Apparatus: – a) 100ml measuring cylinder b) 10ml measuring cylinder c) Test tube d) Stopwatch e) Magnesium ribbon f) Hydrochloric acid g) Safety goggles h) Water tub i) Retort stand j) Glass tube for collected acid k) Pencil for winding magnesium Diagram: Instructions: 1. Firstly you have to set up the equipment. 2. Fill up the water tub to about three thirds with water or whatever amount you want as long as the gas doesn’t escape. 3.