Investigating the effect of concentration of acid on the
Rate of reaction
Plan
Method
For my experiment, I will be investigating rate of reaction, I will do this using HCl (hydrochloric Acid) and limestone chips (CaCO3) there are many variables that can affect the rate of reaction, they are – Surface area of marble chips, strength of acid, temperature. The quicker that the CO2 (Carbon Dioxide) is produced, the quicker the rate of reaction between them is. For my investigation I will investigate how the strength of acid affects this reaction, I will use 5 strengths of acid, 0.25 Molar, 0.5 Molar, 1.0 Molar, 1.5. Molar and 2.0 molar, for a control I will use 0 Molar acid, or water, I would expect the rate of reaction to be zero for this, and it will only be used to prove that it is the acid that is reacting with the chips, not another variable. I will pour the acid into a conical flask with the marble chips. I will then collect the CO2 released in a measuring cylinder as shown in the diagram below. Alternatively, I could use a gas syringe, but these are expensive, and fragile. So instead I will use a plastic measuring cylinder. I will take readings at intervals of 10 seconds for a set period of time or until the reaction has stopped.
Diagram
Prediction
My Hypothesis is that the higher the concentration of acid, the faster the rate of reaction. This is because the higher the concentration of acid, the more particles of HCl will be colliding with the marble chip which means that there are more reactions taking place, so more CO2 will be produced. I will also predict that the rate of reaction should double if concentration is doubled; this means that for instance it takes 1.0 Molar Acid 50 seconds to create 100cm³ it should then take 2.0 molar acid 25 seconds to create the same volume of gas. My hypothesis is supported by the collision theory. The collision theory is a principle concerned with rates of reaction. During reactions, there is a solution of the reactant and the reactor, in the case of this experiment, the marble chips and the hydrochloric acid respectively. During the reaction, particles from each hit each other and release energy. This is the reaction; it will release the energy as heat. The formula for the reaction is CaCO3+ 2HCl= CaCl2+ H2O+ CO2. So the reaction will give of water and carbon dioxide, the carbon dioxide is the reason that there are bubbles appearing around the marble chips. As the gas is produced, since the conical flask is full of air, the carbon dioxide produced will force gas out of the conical flask, through the delivery tube, and into the up turned measuring cylinder, as the cylinder is full of water, it will “push” the water out. By reading the volume of gas produced, you can see how fast the marble chips and HCl are reacting.
