Chapter 2b

Question 1

What is the formula for rate of a reaction?

Answer 1

Amount of reactant used/ amount of product formed
________________________________________________________
Time

Question 2

State the different ways used to measure rates of reaction

Answer 2

Precipitation
Change in mass
Volume of gas given off

Question 3

Explain collision theory with regards to increasing temperature

Answer 3

When the temperature is increased the particles all moe quicker, if they’re moving quicker they’re going. To collide more often

Question 4

Explain collision theory with regards to higher concentration

Answer 4

If a solution is made more concentrated it means there are more particles of he reactant which makes collisions between important particles more likely

Question 5

Explain collision theory with regards to larger surface area

Answer 5

If one of the reactants is a solid hen breaking it up into smaller pieces will increase the total surface area if the particles have more area to work on there will be more frequent collisions

Question 6

Define activation energy

Answer 6

The minimum amount of energy needed for the particles to react (reactions only happen if the particles collide with enough energy

Question 7

What is a catalyst?

Answer 7

A substance that speeds up a reaction without being changed or used up in the reaction

Question 8

How are catalysts useful in industry?

Answer 8

• because the reaction is quicker it saves money
• allows the reaction to work at lower temperatures which reduces the energy used in a reaction
  Can be used over and over again

Question 9

State some disadvantages of catalysts

Answer 9

Expensive to buy
Different reactions use different catalysts
Catalysts can be ‘poisoned’ by impurities so they can stop working
Reaction must be kept clean

Question 10

What happens in exothermic reactions?

Answer 10

Heat is given out to the surroundings they warm up

E.g combustion, hand warmers and self heating cans

Question 11

What happens in endothermic reactions ?

Answer 11

Heat is taken in by the surroundings, they become cold

E.g thermal decomposition and sports injury packs

Question 12

Define anhydrous

Answer 12

Without water

Question 13

What pH do acids have?

What colour do they turn?

Answer 13

pH 0-6

Red-orange-yellow

Question 14

What pH do alkalis have?

Answer 14

pH 8-14

Blue- purple

Question 15

What pH is neutral?

Answer 15

pH 7

Green

Question 16

Describe the properties of an acid

Answer 16

pH less than 7

Form h+ ions in water

Question 17

Describe the properties of alkalis

Answer 17

A base that dissolves in water

Form OH- ions in water

Question 18

Acid + base =

H+ + OH-

Answer 18

Acid + base —->Salt + water

H+ + OH- —-> H2O

Question 19

What is the state symbol of

a) a solid
b) a liquid
c) a gas
d) aqueous

Answer 19

s
l
g
aq

Question 20

Acid + metal =

Answer 20

Metal salt + hydrogen

Question 21

What kind of salts would hydrochloride acid produce

Answer 21

Chloride salts

Question 22

What kind off salts would sulfuric acid produce?

Answer 22

Sulfate salts

Question 23

Acid + metal oxide=

Answer 23

Salt + water

Question 24

Acid + metal hydroxide =

Answer 24

Salt + water

Question 25

Hydrochloric acid + copper oxide=

Answer 25

Copper chloride + water

Question 26

Nitric acid + potassium hydroxide =

Answer 26

Potassium nitrate + water

Question 27

What four things does the rate of reaction depend on?

Answer 27

Temperature Concentration Catalyst Surface area

Question 28

Define electrolysis?

Answer 28

Splitting up using electricity (If you pass an electric current through an ionic substance that's molten or in a solution it breaks down into the element it's made of)

Question 29

Describe electrolysis

Answer 29

- it requires a liquid (electrolyte) to conduct electricity - electrolytes contain free ions which allows electricity - flow of electrons is needed ( electrons taken away at the positive electrode and given at the negative electrode)

Question 30

Describe electrolysis of lead bromide

Answer 30

- At the negative electrode one lead ion accepts two electrons to become one lead atom - at the positive electrode two bromide ions loose one electron each and becomes one bromine molecules

Question 31

Describe how electrolysis is used to extract aluminium from its ore

Answer 31

1) aluminums ore (bauxite) very abundant with metal 2) after mining and purifying a white powder is left 3) this is pure aluminium oxide Al2O3 4) aluminium is extracted from this using electrolysis

Question 32

How is cryolite used to lower the temperature (and costs)

Answer 32

-Aluminium has a very high melting point (over 2000 degrees) So melting it would be very expensive -The aluminium is dissolved in molten cryolite which brings down the temperature -The electrodes are made out of carbon (good conductor of electricity) - aluminium forms at the negative electrode and oxygen at the positive one

Question 33

How does electroplating work?

Answer 33

- electroplating used electrolysis to coat the surface of one metal with another metal - the negative electrode is the one you want to plate and the positive electrode is the pure metal you want it to be plated with

Question 34

How would you electroplated silver onto a brass cup?

Answer 34

* The brass cup would be the negative electrode (to attract positive silver ions) * A lump of pure silver at the positive electrode and dip them into a solution of silver ions e.g. Silver nitrate

Question 35

Uses of electroplating?

Answer 35

- decoration | - conduction

Question 36

How do you make soluble salts using a metal or an insoluble base?

Answer 36

You need the right acid + a metal or an insoluble base Add the metal, metal oxide or hydroxide to the acid, the solid will dissolve in the acid as it reacts. (The excess solid will sink to the bottom when the base is neutralised) Filter out the excess metal Evaporate some of the water then leave the rest to evaporate slowly this is called crystallisation

Question 37

How do you make soluble salts using an alkali?

Answer 37

- Add exactly the right amount of alkali to just neutralise the acid then repeat using exactly the same volumes of alkali and acid so the salt isn't contaminated with the indicator - just evaporate off the water to crystallise as normal

Question 38

Describe precipitation reactions (when making insoluble salts)

Answer 38

1) if the salt is insoluble precipitation reactions are useful 2) pick two solutions containing the ions you need 3) once the salt has precipitated out filter it from the solution