Reaction Rates

Question 1

iron rusting

Answer 1

Very slow

Question 2

Wood burning

Answer 2

Slow

Question 3

Magnesium and acid

Answer 3

Medium speed

Question 4

Magnesium burning

Answer 4

Fast

Question 5

Marble and acid

Answer 5

Fast

Question 6

Gas burning

Answer 6

Very fast

Question 7

Chalk and acid

Answer 7

Very fast

Question 8

Equation for reaction rate

Answer 8

Amount of chemical made or used up (g or cmcubed) / time taken (s)

Question 9

Units for reaction rate

Answer 9

g/s or cm3/s

Question 10

Word equation for magnesium and hydrochloric acid

Answer 10

Magnesium + hydrochloric acid —> magnesium chloride + hydrogen

Question 11

What does a steep line on a graph mean?

Answer 11

Fast reaction

Question 12

What does a less steep line on a graph mean?

Answer 12

Slower reaction

Question 13

What does a flat line on a graph mean?

Answer 13

Reaction finished

Question 14

Burning nail iron (to form iron oxide)

Answer 14

Glowed red, turned darker grey
Slowest reaction

Question 15

Burning iron wool (to form iron oxide)

Answer 15

Some sparks, glows brighter
Medium reaction

Question 16

Burning iron filings (to form iron oxide)

Answer 16

Fast, sparkly reaction
Fastest reaction

Question 17

What do smaller particles have?

Answer 17

Bigger surface areas

Question 18

What do bigger particles have?

Answer 18

Small surface areas

Question 19

What does a larger surface area mean?

Answer 19

More atoms are exposed and available to react with other atoms

Question 20

Do smaller particles react slowly or quickly?

Answer 20

Quickly - faster than large particles

Question 21

Equation for marble chips and hydrochloric acid

Answer 21

2HCl(aq) + CaCO3(s) —> CaCl2(aq) + H2O(l) + CO2(g)

Question 22

Why does the mass of the flask change (marble chips and hydrochloric acid)?

Answer 22

It looses carbon dioxide

Question 23

Word equation for calcium carbonate and hydrochloric acid

Answer 23

Calcium carbonate + hydrochloric acid —> calcium chloride + water + carbon dioxide

Question 24

Word equation for sodium thiosulphate and hydrochloric acid

Answer 24

Sodium thiosulphate + hydrochloric acid —> sodium chloride + water + sulphur + sulphur dioxide

Question 25

Effect of particles size (large particles)

Answer 25

SMALL surface area LESS frequent collisions SLOW reaction - only iron atoms on surface can react

Question 26

Effect of particle size (smaller particles)

Answer 26

LARGE surface area MORE frequent collisions FAST reaction - more iron atoms are exposed and ready to react

Question 27

Effect on concentration (low concentration)

Answer 27

FEW particles per unit volume LESS frequent collisions SLOW reaction

Question 28

Effect on concentration (high concentration)

Answer 28

MANY particles per unit volume MORE frequent collisions FAST reaction

Question 29

Effect of pressure (low pressure)

Answer 29

FEW particles per unit volume LESS frequent collisions SLOW reaction

Question 30

Effect of pressure (high pressure)

Answer 30

MANY particles per unit volume MORE frequent collisions FAST reaction

Question 31

Effect of temperature (low temperature)

Answer 31

SLOWER particles LESS frequent collisions LESS successful collisions LESS energetic collisions (FEWER collisions above activation energy) SLOW reaction

Question 32

Effect of temperature (high temperature)

Answer 32

FASTER particles MORE frequent collisions MORE successful collisions MORE energetic collisions (MORE collisions above activation energy) FAST reaction

Question 33

What is the collision theory?

Answer 33

For particles to react, they have to collide with sufficient energy (the activation energy)

Question 34

What is activation energy?

Answer 34

The minimum amount of energy required for a reaction to take place

Question 35

What is a catalyst?

Answer 35

A substance that speeds up a chemical reaction without being used up

Question 36

Examples of catalysts:

Answer 36

Nickel Enzymes Cobalt

Question 37

What metals make good catalysts?

Answer 37

Transition metals

Question 38

Which catalyst is the most effective (catalysing the decomposition of hydrogen peroxide)

Answer 38

Magnese dioxide

Question 39

How do catalysts work?

Answer 39

Provide an alternative reaction pathway with a lower activation energy

Question 40

Uses of catalysts:

Answer 40

Catalytic converters Glues (araldite) and car body fillers Making margarine Making some plastics Enzymes are biological catalysts

Question 41

What does a catalyst providing an alternative reaction pathway with a lower activation energy mean?

Answer 41

Less energy is needed for collisions to be effective Therefore, when particles collide, more of the collisions are effective and the rate increases