Rates of Reaction and Energy Changes

Question 1

what is the method when investigating the effects of changing the conditions of a reaction on the rates of chemical reactions? observing colour change.

Answer 1

1. measure fixed volumes of sodium thiosulfate and hydrochloric acid
2. hear both solutions in water bath
3. mix them
4. place over cross, wait for cross to disappear, cloudy
5. repeat at different temperatures
6. depth, volume, concentration must stay the same

Question 2

what is the method when investigating the effects of changing the conditions of a reaction on the rates of chemical reactions? surface area or amount of gas produced.

Answer 2

1. place marble chips with hydrochloric acid
2. measure volume of gas produced in gas syringe
3. take recordings at regular intervals
4. plot results
5. repeat with crushed marble chips
6. compare results

Question 3

what is the equation to measure rate of reaction?

Answer 3

amount of reactant used or amount of products formed / time

Question 4

what caused ratio reaction to increase?

Answer 4

• when particles collide
• more frequent collisions speed it up
• or energy of collisions speed it up

Question 5

what does more concentrated/pressure mean?

Answer 5

higher rate

Question 6

what does higher temperature mean?

Answer 6

higher rate

Question 7

what does larger surface area mean?

Answer 7

higher rate

Question 8

what is a catalyst?

Answer 8

substance that speeds up the rate of a reaction without being chemically changed or used up

Question 9

what is activation energy?

Answer 9

minimum energy that particles need when they collide

Question 10

how does the addition of a catalyst increase the rate of a reaction?

Answer 10

• decrease activation energy
• provide alternative reaction pathway
• so each particle has the least minimum amount of energy needed for a reaction to take place.

Question 11

what are enzymes?

Answer 11

biological catalysts and are used int eh production of alcoholic drinks

Question 12

what do changes in heat energy accompany?

Answer 12

salts dissolving in water
neutralisation reactions
displacement reactions
precipitation reactions

Question 13

what is an exothermic reaction?

Answer 13

energy is given out usually heat

Question 14

what is an endothermic reaction?

Answer 14

energy is taken in usually heat

Question 15

what kind of reaction is that breaking of bonds?

Answer 15

endothermic

Question 16

what kind of reaction is the making of bonds?

Answer 16

exothermic

Question 17

what is the equation for bond energy?

Answer 17

overall energy change= energy required to break bonds - energy released by forming bonds

Question 18

what is overall energy changed measured in?

Answer 18

KJ mol-1