Rates of Reaction and Energy Changes

Question 1

What is the equation for ROR?

Answer 1

Rate of reaction= Amount of reactant used or product formed/ time

Question 2

How can you measure the ROR when a precipitate is formed?

Answer 2

Put a black cross below a beaker containing 1 reactant and time how long it takes for cross to disappear after 2nd reactant added.

Question 3

Define “activation energy”

Answer 3

Minimum amount of energy required for a reaction to occur between two reacting particles.

Question 4

What must happen for a reaction to occur?

Answer 4

Particles must collide at correct orientation with enough energy to react.

Question 5

In terms of particles, what 2 things could happen when ROR increases?

Answer 5

More frequent collisions and energy of collision increase.

Question 6

How can the ROR be increased?

Answer 6

Increasing:
Temperature
Concentration 
SA/ V ratio 
Add a catalyst

Question 7

How does temp affect ROR?

Answer 7

Increases it because reactants have more activation energy and more successful collisions.

Question 8

How does SA affect ROR?

Answer 8

Increases it because a bigger SA means more exposed particles so more frequent, successful collisions.

Question 9

How does a catalyst affect ROR?

Answer 9

Increases it because it provides an alternate reaction pathway with a lower activation energy. More particles have enough energy to overcome activation energy, more successful collisions.

Question 10

How does concentration affect ROR?

Answer 10

Increases it because there are more reacting particles in the same volume so more frequent collisions.

Question 11

A graph showing time and amount of gas given off during experiment has a steep gradient? What ROR is it?

Answer 11

Fast

Question 12

Define catalyst

Answer 12

A substance which speeds up rate of a reaction without being chemically changed at the end.

Question 13

How does a catalyst speed up ROR?

Answer 13

Provides an alternate reaction pathway with a lower activation energy.

Question 14

Define an enzyme

Answer 14

Enzymes are biological catalysts that increase RORs in living cells.

Question 15

Define ENDOTHERMIC

Answer 15

A reaction that takes place in heat energy from surroundings.

Question 16

Define EXOTHERMIC

Answer 16

A reaction that gives out energy to the surroundings.

Question 17

Are displacement reactions endothermic or exothermic?

Answer 17

Either

Question 18

Give an example of an endothermic reaction

Answer 18

Photosynthesis

Question 19

All elements in a group have the same number of _____ in their _____ shell.

Answer 19

Electrons, outer

Question 20

Do alkali metals become more or less reactive as you go down the group?

Answer 20

More

Question 21

All alkali metals react with water to produce…

Answer 21

Metal hydroxide and hydrogen

Question 22

What would you expect to see when lithium reacts with water?

Answer 22

Fizzing

Question 23

We don’t use caesium or rubidium in school because they…

Answer 23

Are too corrosive

Question 24

Do halogens become more or less reactive as you go down the group?

Answer 24

Less

Question 25

What happens to the colour of halogens as you go down the group?

Answer 25

They become darker

Question 26

How do the states of matter change in halogens as you go down the group?

Answer 26

They increase and therefore become more solid.

Question 27

What is the word equation for the reaction of hydrogen and chlorine?

Answer 27

Hydrogen + chlorine —>hydrogen chloride

Question 28

Why will Chlorine displace bromine from potassium bromide?

Answer 28

Chlorine is more reactive than bromine so it will displace bromine.

Question 29

What is special about the arrangement of noble gases?

Answer 29

They have a full outer shell of electrons.

Question 30

What does “inert” mean?

Answer 30

Doesn’t react with anything

Question 31

What reactions do the noble gases do?

Answer 31

None, they are inert because they have a full outer shell of electrons.

Question 32

Give a use for helium and 2 reasons why.

Answer 32

Airships- inert and therefore don’t catch fire, less dense than air so it will float.

Question 33

All elements in a group have ______ properties

Answer 33

Chemical