Rates of Reaction

IB Chemistry: Rates of Reaction Rates of Reaction Define the term rate of reaction. This is essentially a reaction: Reactants →Product The "concentration" of a reactant decreases as it transforms into a product during a reaction,while the concentration of a product increases. So we can define ‘rate of reaction’ as either: ○ Decrease in concentration of the reactants per unit time. OR ○ Increase in concentration of the products per unit time. Describe suitable experimental procedures for measuring rates of reactions. We can calculate the change in concentration through a variety of methods: ○ Mass Change ○ Volume Changes ○ Change in pH for reactions including acids and bases. ○ Colorimeter for color change. Use these devices to measure the volume produced, and then divided by the amount of timetaken for the reaction to occur to get the rate of reaction Analyse data from rate experiments The graph below shows the rate of reaction of a substance over time. To find the rate of reaction at a certain time, you simply have to find the gradient, which is the change in volume of gas produced divided by the time. I usually use the “tangent method”, where you draw a tangent line which touches the specifictime in which to calculate the rate of reaction. The steeper the line, the faster the rate of reaction. This is because if the reaction graph is steeper, the gradient will have a higher value, and hence the rate of reaction will commence at a faster rate. Example: Which has a faster rate of reaction? Let’s just say the blue line produces 200 g of gas and the red line 150 g. They both do so in 50 seconds.

If we take the gradient, the blue lines rate of reaction is 4 g /sec and the red line 3 g /sec, sothe average rate of reaction will be faster in the red line.