Rates of Reaction

1. 2 Rates of Reaction 5 1 2 3 4 6 10 7 8 9 11 12 13 14 15 16 17 Calderglen High School

2. 1. Describe how the concentration of reactants affects the speed of reaction? As the reactant concentration increases the speed of the reaction increases. Calderglen High School

3. 2. Name FOUR factors which affect the speed (or rate) of a chemical reaction? Particle Size (Surface Area) Temperature Concentration Use of Catalyst Calderglen High School

4. 3. Work out the rate of reaction over the first 20 seconds. Rate = Change in Concentration Change in Time = (0.2 – 0.05) (20 – 0) = 0.15 = 0.0075 mol /l / s 20 mol / l Calderglen High School

5. 4. Describe how particle size affects the speed of reaction? As particle size decreases the speed of reaction increases Calderglen High School

6. 5. Describe how temperature affects the speed of reaction? As temperature increases the speed of reaction increases Calderglen High School

7. 6. What are ENZYMES? Biological catalysts Calderglen High School

8. 7. What is a catalyst? A substance which can speed up a reaction, but is not used up in the reaction and can be recovered chemically unchanged Calderglen High School

9. 8. Why does decreasing the particle size of reactants increase the speed of reaction? Smaller particles give a bigger surface area. This results in more collisions between reactants and therefore faster reactions Calderglen High School

10. 9. Work out the rate of reaction between 20 and 40 seconds. Rate = Change in Volume Change in Time = (41 – 29) (40 – 20) = 12 20 = 0.6 cm3 / s Calderglen High School

11. 10. What must be controlled when carrying out experiments to compare speeds of reaction? All variables other than the one being tested must be kept the same in all experiments Calderglen High School

12. 11. What is a VARIABLE? Any factor in an experiment which can be changed or varied. e.g. concentration or temperature of the solution used Calderglen High School

13. 12. Give everyday examples of uses of catalysts? Transition metals in car catalytic converters. Calderglen High School

14. 13. Rates Experiments • Which two of the following experiments could be used to find the effect of changing the particle size? Calderglen High School

15. A B 2M hydrochloric acid at 150C 2g of small chalk lumps 2g of small chalk lumps D answer 1M hydrochloric acid at 250C 2g of small chalk lumps 2g of large chalk lump 2M hydrochloric acid at 250C C 2M hydrochloric acid at 250C Calderglen High School

16. 14. Rates Experiments • Which two of the following experiments could be used to find the effect of changing the concentration of the acid? Calderglen High School

17. A B 2M hydrochloric acid at 250C 2M hydrochloric acid at 150C 2g of small chalk lumps 2g of small chalk lumps D C answer 1M hydrochloric acid at 250C 2M hydrochloric acid at 250C 2g of small chalk lumps 2g of large chalk lump Calderglen High School

18. 15. Rates Experiments • Which two of the following experiments could be used to find the effect of changing the temperature of the acid? Calderglen High School

19. A B 2M hydrochloric acid at 250C 2M hydrochloric acid at 150C 2g of small chalk lumps 2g of small chalk lumps D C answer 1M hydrochloric acid at 250C 2M hydrochloric acid at 250C 2g of small chalk lumps 2g of large chalk lump Calderglen High School

20. 16. What does EXOTHERMIC mean? Heat energy is given out in a reaction. Calderglen High School

21. 17. Two chemical react in a test tube. The temperature goes down. Is the reaction EXOTHERMIC or ENDOTHERMIC? ENDOTHERMIC (heat energy is taken in by the reaction, this makes the surrounding temperature fall). Calderglen High School