Rates of Reactions - Part 1

In this video you are going to learn what the reaction rate is and some ways of measuring reaction rate. Reaction rate is a measure of how quickly the reactants in a reaction change into the products of the reaction. The rate of a chemical reaction can be measured in two ways: 1) The first way is to measure how quickly the reactants (the substances on the left of the arrow in the equation) decrease. 2) The second way is to measure how quickly the products (the substances on the right of the arrow in the equation) increase. Example for 1: Measuring how quickly reactants decrease. We will look at the reaction between marble chips (calcium carbonate) and hydrochloric acid. As the reaction proceeds, the reactants lose mass because carbon dioxide gas is given off. We can measure the decrease in mass of reactants by using this type of apparatus with a conical flask stopwatch, cotton wool plug and balance. Based on our measurements, we plot a graph of ‘mass of reactants against time’. The rate of reaction at point A is given by the gradient at A which is y/x and the rate of reaction at point B is given by the gradient at point B which is y’/x’ . Example for 2: Instead of measuring the loss of mass of the reactant we can also measure the gain in volume of the product carbon dioxide.