The Rate And Extent Of Chemical Change

Question 1

Rate of reaction equation

Answer 1

Amount of reactant used or product formed/

Time

Question 2

Measuring the amount of reactants used

Answer 2

If one of the products is a gas measure the mass in grams of the reaction mixture before and after the reaction takes place and the time it takes for the reaction to happen
The mass of the mixture will decrease
The units for the rate of reaction g/s
Amount of reactant can also be measured in moles
As the reaction takes place the reactant is used up So the amount of reactant remaining decreases
Concentration of the reactants is calculated as the amount divided by the volume of the reaction mixture it is measured in units of mol/dm^3

Question 3

Measuring the amount of product formed

Answer 3

If one of the products is a gas measure the total volume of gas produced in cubic centimetres with a gas syringe and the time it takes for the reaction to happen

Question 4

Measuring the time it takes for reaction mixture to become opaque or change colour

Answer 4

Time how long it takes for the mixture to change colour
Rate of reaction =

1/
Time taken for solution to change colour

Question 5

Chemical reactions only occur when

Answer 5

Reacting particles collide with each other with sufficient energy

Question 6

Activation energy

Answer 6

The minimum amount of energy required to cause reaction

Question 7

Four factors affecting the rate of reaction

Answer 7

Temperature
Conc
Surface area
Catalysts

Question 8

How temperature affects reactions

Answer 8

When it’s not they move quicker so collide more with greater energy

Question 9

Concentration affecting reactions

Answer 9

Higher conc particles are closer together collide more often
Increasing pressure also increases collision

Question 10

Required practical

Answer 10

Pg 11

Question 11

Surface area affect reaction

Answer 11

Small pieces have larger surface area

More particles exposed for collision

Question 12

Graphs can show

Answer 12

The progress of a chemical reaction

Question 13

3 things to remember on a graph

Answer 13

Steeper line - faster reaction
When one of the reactants is used up, the reaction stops (line becomes horizontal)
Same amount of product is formed form the same amount of reactants, regardless rate

Question 14

To find rate of reaction at a particular time on a graph

Answer 14

Draw a tangent to the curve at the time
Find gradient of tangent
Gradient= rate of reaction at that time

Question 15

Catalyst

Answer 15

Substance that increases the rate of a chemical reaction without being used up

Eg in industry

Iron
Broken pottery

Not include in chemical equation

Question 16

A catalyst can

Answer 16

Reduce the amount of energy needed for a collision
Makes more successful collisions
Speeds up reaction
Provides a surface for the molecules to attach to, increases their chances of collision

Question 17

Catalyst In biological systems

Answer 17

Enzymes

Question 18

Cracking of hydrocarbon catalyst

Answer 18

Broken pottery

Question 19

Manufacture of ammonia catalyst

Answer 19

Iron

Question 20

Increasing rate of reaction is useful in industry because

Answer 20

It reduced cost

Question 21

Reversible

Answer 21

Can go forwards and back

The products can react to produce the original reactants

Question 22

Example of reversible reaction

Answer 22

Solid ammonia chloride decomposes when heated to produce ammonia and hydrogen chloride gas

Ammonia reacts with hydrogen chloride to produce clouds of white ammonia chloride

Question 23

The direction of reversible reaction can be changed by

Answer 23

Changing the conditions

Question 24

If a reversible reaction is exothermic in One Direction

Answer 24

It is endothermic in the other

Question 25

The amount of energy given out in the exothermic reaction is the same

Answer 25

As the amount of energy taken in during the endothermic reaction

Question 26

In a closed system

Answer 26

No reactants are added and no products are removed

Question 27

When a reversible reaction occurs in a closed system

Answer 27

And equilibrium is achieved

Question 28

The relative amounts of all the reacting substances at equilibrium depends up

Answer 28

The conditions of the reaction

Question 29

Le Chateliers principle states

Answer 29

If a system in equilibrium is subjected to a change in conditions then the system shifts to resist the change

Question 30

Exothermic reaction

Answer 30

If the temperature rises the yield decreases

If the temperature lowers the yield increases

Question 31

Endothermic reactions

Answer 31

If the temperature rises the yield increases

If the temperature lowers the yield decreases

Question 32

Changing reaction conditions

In reactions involving gases

Answer 32

Increase in pressure favours the reaction that produces the least number of gas molecules
Decrease in pressure favours the reaction that produces the greater number of gas molecules

Question 33

Changing reaction conditions

If the concentration of a reactant or product is changed

Answer 33

The system is no longer in equilibrium

The system adjusts until it can reach equilibrium once more