Topic 4

Question 1

Predict how position of dynamic equilibrium is affected by changes in temperature

Answer 1

• if decrease, equilibrium move in exothermic direction to produce more heat
• if increase, equilibrium move in endothermic direction to absorb extra heat

Question 2

Predict how position of dynamic equilibrium is affected by changes in pressure

Answer 2

• if increase, equilibrium move towards side that has fewer moles of gas to reduce pressure
• if decrease, equilibrium move towards side with more moles of gas to increase pressure

Question 3

Predict how position of dynamic equilibrium is affected by changes in concentration

Answer 3

• if increase of reactants, equilibrium move to right to use up reactants making more products
• if increase of products, equilibrium move to left to use up products making more reactants
• if decrease opposite effect

Question 4

Recall conditions for the Haber process

Answer 4

• temp 450°c
• pressure 200 atmospheres
• iron catalyst

Question 5

Describe the formation of ammonia

Answer 5

A reversible reaction between nitrogen (extracted from air) and hydrogen(obtained from natural gas) to form ammonia. It can reach a dynamic equilibrium

Question 6

Define dynamic equilibrium

Answer 6

When forward and backward reactions are both happening at same time and same rate, and concentrations of reactant and products have reached a balance and won’t change

Question 7

deduce the relative reactivity of some metals by their reaction with water

Answer 7

very reactive metals will react vigorously with water, less reactive metals won’t react much with cold water, but will react with steam, copper won’t react with steam or water

Question 8

deduce the relative reactivity of some metals by their reaction with acids

Answer 8

more reactive metal is, faster the reaction with acid will go. very reactive metals will fizz vigorously, less reactive metals will bubble a bit , unreactive metals won’t react with dilute acids at all

Question 9

explain displacement reactions

Answer 9

are redox reaction, where a more reactive elements reacts to take the place of a less reactive metal in a compound. more reactive metal loses electrons(oxidised), less reactive metal gains electrons(reduced)

Question 10

what is oxidation and reduction in terms of electrons

Answer 10

Oxidation
Is
Loss
Reduction
Is
Gain

Question 11

what is oxidation and reduction in terms of oxygen

Answer 11

oxidation gain oxygen

reduction loss of oxygen

Question 12

describe chemical reactions and what can be changed by changing reaction conditions

Answer 12

chemical reactions are reversible, the use of symbol ⇌ in equations and direction of some reactions can be altered by changing reaction conditions

Question 13

where are metals found in the earth

Answer 13

• most metals extracted from ores found in earth’s crust
• unreactive metals found in earth’s crust as the uncombined elements
• extraction of metals involves reduction of ores

Question 14

list the reactivity series in order from least to most reactive

Answer 14

Gold, silver, copper, hydrogen, iron, zinc, carbon, aluminium, magnesium, calcium, sodium, potassium

Question 15

describe the reactivity series in terms of reactivity of metals with water and dilute acids

Answer 15

if metal below hydrogen in reactivity series, it’s less reactive than hydrogen and won’t react with dilute acids

Question 16

describe how these reactions show the relative tendency for of metal atoms to form cations

Answer 16

metals at bottom of reactivity series less reactive- don’t give up their electrons to form cations easily. and are more resistant to corrosion

Question 17

explain how some metals can be extracted by reduction with carbon

Answer 17

metals below carbon in reactivity series can be extracted by reduction using carbon, because carbon can only take oxygen away from metals less reactive than itself

Question 18

give an example of reduction using carbon

Answer 18

iron oxide is reduced in blast furnace to make iron

Question 19

explain how some metals can be extracted by electrolysis

Answer 19

metals more reactive than carbon extracted using electrolysis of molten compounds. once metal ore melted, electric current passed through it, metal discharged at cathode and non-metal at anode

Question 20

give an example of electrolysis

Answer 20

aluminium extracted from ore using electrolysis with carbon electrodes. aluminium oxide has high melting point so ore first dissolved in molten cryolite to lower melting point. aluminium formed at cathode and oxygen at anode

Question 21

describe Bioleaching as a bacterial method of extracting metals

Answer 21

uses bacteria to separate metals from their ores. bacteria get energy from bonds between atoms in ore, separating out metal from ore in process. the leachate contains metal ions, which extracted by electrolysis or displacement

Question 22

describe Phytoextraction as a method of extracting metals

Answer 22

involves growing plants in soil containing metal compounds. plants can’t use or get rid of metals so they gradually build up in the leaves. plants harvested, dried and burned in furnace. ash contains metal compounds from which metals extracted by electrolysis or displacement reactions

Question 23

explain the advantages of recycling metals

Answer 23

• saves money
• beneficial to economy to recycle metals expensive to extract or buy
• massive industry, creates lots of jobs
• cuts down amount of rubbish sent to landfill
• preserves supply of valuable raw materials

Question 24

describe the choice of material as a stage in a life cycle assessment

Answer 24

• metals have to be mined and extracted from ores, processes need lots energy and cause lots pollution
• raw materials for chemical manufacture often come fro crude oil, non-renewable resource

Question 25

describe the manufacturing of product as a stage in a life cycle assessment

Answer 25

• uses a lot of energy and other resources
• lots pollution
• need to think of how to dispose of any waste products
• some waste recycled and turned into other useful chemicals
• most chemical manufacture needs water, businesses ave to make sure don’t put polluted water back into environment

Question 26

describe the product use as a stage in a life cycle assessment

Answer 26

• using product can damage environment;
  
  • paint gives off toxic fumes
  • burning fuels releases greenhouse gases and other harmful substances
  • fertilisers an leach into streams and rivers and cause damage to ecosystems

Question 27

describe the disposal as a stage in a life cycle assessment

Answer 27

• product often disposed of in landfill site at end of life
• takes up space and can pollute land and water
• products might be incinerated, causes air pollution