rate of reaction test revision Flashcards
what is rate of reaction
a measure of how quickly products are formed, or how quickly reactants are used up in a chemical reaction
what are ways we can measure rate of reaction
volume of gas produced, mass lost or time taken for a colour change
how do we calculate rate of reaction
change of mass, volume etc divided by time taken. Units would be the units for those ↑per second. e.g. cm/second
how to calculate rate over a period time (say 20secs etc) using a graph
change in y divided by change in x. e.g. 40cm of gas produced in a reaction, divided by time taken, like 20 seconds
how to calculate the rate of reaction at an exact point on a graph
find ur point on the graph, and draw a straight line across it, with equal angles on either side. Find 2 points on the graph which are easy numbers. Using those points, find the change in y and the change in x, and divide change in y by change in x. This is the rate
Definition of concentration
The number of particles per unit volume
An experiment investigating the effect of concentration, on rate of reaction
Set up multiple experiments, with varying levels of the reactants, or reactant. When changing the amount of reactants, make sure to keep the volume the same, by adding water, which won’t affect the reaction. For example, seeing how long it takes different concentrations of Sodium Thiosulphate and Hydrochloric acid to turn cloudy, or different concentrations of HCl, and marble chips, using how much gas is produced as a way of measuring rate.
An experiment investigating the effect of surface area on rate of reaction
Set up multiple experiments, with different sizes of the reactants. For example, large, small and powdered marble chips.
An example of how temperature affects rate
Set up multiple experiments, each heated to a different temperature. An example of such a reaction you could use, is the reaction between potassium permanganate and glucose. Potassium permanganate is purple, and so we use its color change to go colorless as a way of measuring rate.
Define the term activation energy
The minimum amount of energy required for a reaction to take place
What is a catalyst
A catalyst provides an alternative pathway for a reaction, with a lower activation energy.
How does concentration affect rate of reaction
A reaction happens because of successful collisions between reactant particles. When the concentration of the reactants is higher, there are more reactant particles per unit of volume, so there are more collisions, meaning there’s a higher chance for successful collisions.The sooner there are enough successful collisions, the faster the reaction happens.
How does surface area affect rate of reaction
As the surface area increases, the rate of reaction increases because there are more particles available for collisions increasing the frequency of successful collisions which will therefore increase the rate of reaction
How does temperature affect rate of reaction
Temperature is the most effective way of increasing the rate of reaction. When the particles are hotter, they have more energy, which is converted to kinetic energy, so they move faster. This means that there are more frequent collisions, increasing chances of frequent collisions. As well as this, the increased temperature provides them energy, meaning that they have more energy than activation energy. This means it takes less time to react.
How do catalysts affect the rate of reaction
Catalysts provide an alternate pathway for particles, with a lower activation energy. This means that more particles will produce an amount of energy above the activation energy when they collide, allowing for more successful collisions, and increasing rate of reaction.
