Polymerisation : Rates of reaction 3.9-3.11
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3.9 Describe the experiment used to investigate changes in surface area of a solid in terms of rate of reaction:
• Set up a conical flask attached to a gas syringe via tubing coming from the bung on the conical flask • Add dilute HCL and marble chips in it , • Measure the volume of gas produced using a gas syringe . Take readings at regular intervels and record results in table • Repeat the experiment with the same volume and concentration of acid, and exactly the same mass of marble chips but with it more scrunched up . • Repeat same with powderd chalk as marble and chalk is both calcium carbonate
3.9 Describe the experiment used to investigate changes in temperature of a solution in terms of rates of reaction:
• Sodium thisulphate + HCl are both clear solutions –> when reacted together they then form a yellow precipitate of sulphur • You can measure rate of reaction by placing a black X mark under the flask and watching how long it takes for the black cross to dissapear due to the solution becoming too cloudy. • The reaction can be repeated with other temperatures. It is best to heat the heat the acids in a water bath before. • Depth of liquid must be kept the same. • The higher the temp, the faster the cross will disappear, due to the faster rate of reaction. • You can then compare the timings for each temperature.
3.10 How does change in surface area influence the rate of a reaction?
• Breaking a solid into smaller pieces - increasing the surface area : volume ratio - increases the rate of reaction. • This is as there is an increased frequency of collisons between the solution and solid particles. Therefore, the frequency of successful collisions increases, increasing the rate of reaction. • More of the solid’s particles are exposed at the surface and available to react
3.10 How does temperature influence the rate of reaction?
• Increasing temperature increases the average kinetic energy of the particles. • This means the average speed of the particles increases. • This means there is a greater frequency of collisions which are successful. • And a greater proportion of the collisions have the required activation erergy(Ea). • This results in the rate of reaction increasing.
3.10 How does the concentration of a solution change the rate of reaction?
• When a solution has a higher concentration, it has more reactant particles per unit volume. • This as a result increases the frequency of collisions, increasing the frequency of successful collision, increasing the rate of reaction.
3.10 How does the pressure of a gas change the rate of reaction?
• There is a higher number of reactant particles per unit volume. • This results in a higher frequency of collisions and therefore, a higher frequency of successful collisions, increasing the rate of reaction.
3.10 How does the use of a catalyst influence the rate of reaction?
• Catalysts work by lower the activation energy(Ea) for a reaction to start. • Catalysts lower Ea by finding an alternative reaction pathway to start a reaction. • This route is done by breaking/making bonds in completly different way. • This alternative reaction pathway has a lower Ea therefore, increasing the rate of reaction
What is activation energy?
The minimum energy required for particles to react.