Write an experiment to prove that
temperature influence the rate of
reaction.
Answers
Explanation:
Factors affecting the rates of Reaction - theory and methods of measuring the speed of a reaction (c) Doc Brown
(i) The above diagram illustrates how you can investigate how varying the temperature affects the rate at which it reacts with a given quantity of limestone granules - but water bath not shown.
The apparatus set-up illustrated above is fine for an initial room temperature base-line experiment, but for higher temperatures, its a bit tricky - some ideas are described with another diagram further down the page.
calcium carbonate (marble chips) + hydrochloric acid ==> calcium chloride + water + carbon dioxide
CaCO3(s) + 2HCl(aq) ===> CaCl2(aq) + H2O(l) + CO2(g)
In the diagram above, the white 'blobs' represent carbon dioxide gas being evolved and the grey lumps the limestone chips, granules or powder.
You follow the reaction by measuring the volume of carbon dioxide formed using the gas syringe system.
You must keep the following variables constant - the volume of hydrochloric acid, the mass of limestone AND its particle size, the concentration of the hydrochloric acid and TRY to keep a gentle constant stirring rate as you are noting down the time and volume of carbon dioxide gas formed.
Gentle stirring (swirling action) is important, if you don't, the bottom layers of acid become depleted in acid giving a falsely slow rate of reaction.
So, the only factor you should vary in the temperature of the reactants and flask.
You repeat the experiment at different temperatures to see the effect of temperature on the rate-speed of the reaction between hydrochloric acid and limestone/marble chips-powder.
Keeping the temperature constant, particularly at temperatures above room temperature (ambient temperature), is quite a problem which is best solved by using a thermostatically controlled large water bath.
The flask and gas syringe system for measuring the rate of a chemical reaction.
If you have access to a thermostated water bath in which to the different temperature experiments, that's great, if not, I've suggested a few ideas below.
Before you had the solid reactant (marble) or a solid catalyst, depending on the experiment, you must allow the conical flask of solution (acid, hydrogen peroxide etc.) to reach the ambient temperature of the water bath.
If no thermostat system is available, there are two simpler, but not as accurate alternatives.
If the experiment doesn't take too long, a large beaker or trough of water might do, its temperature monitored with a thermometer, but still allow time for the conical flask and contents to warm up to the same temperature. Since cooling is taking place all the time you need to warm up the water a few degrees above the desired reaction temperature. You can also warm up the conical flask solution to the same temperature independently. You should take the temperature at the start of the reaction and at the end and use the mean value for your final results table.
You can, least accurately of all, measure the temperature of the solution at the start of the reaction (before adding solid) and re-measure at the end of the experimental time allotted, and use the average temperature. Its not that accurate, but its better than nothing and you should still be able to derive the general trend of how temperature affects the speed-rate of a reaction.
