Chemistry Equations

Front 1

Flocculation
What is added and why?

Back 1

Lime (Ca(OH)2) is added to neutralise acids and provide OH- ions
Alum (aluminium sulfate) added to form a gelatinous precipitate which traps other fine particles

Front 2

Equation for flocculation

Back 2

Al3+(aq) +3OH- (aq) --> Al(OH)3 (s)

Front 3

Desalination methods:

Back 3

Distillation
Reverse Osmosis
Ion exchange

Front 4

Treatment of drinking water: Process

Back 4

1. flocculation
2. Settling of 'floc'
3. Filtering
4. Chlorination

Front 5

Corrosion equation:

Back 5

2Fe(s) + O2 (aq) + 2H2O (l) --> 2Fe2+ (aw) + 4OH- (aq)

Iron is oxidised, oxygen is reduced

Front 6

Protecting against corrosion: what is...
- surface protection
- alloying
- electroplating

Back 6

Surface protection = covering surface of iron with paint, plastic, etc. to prevent contact with oxygen and moisture

Alloying slows rate of corrosion

Electroplating: iron coated with thin layer of different metal which forms a protective oxide coating

Front 7

Protecting against corrosion: what is...
- Cathodic protection
-Sacrificial protection

Back 7

Cathodic: give iron negative charge - becomes cathode. Oxidation inhibited because too many electrons.

Sacrificial: e.g. with Zinc. Zinc oxidizes more readily than iron.

Front 8

Green Chemistry Principles:

Back 8

1. Prevent waste
2. Design safer chemicals and products
3. Design less hazardous methods
4. Use renewable raw materials
5. Use catalysts, not stoichiometric reagents
6. Avoid chemical derivatives (explain!)
7. MAXIMISE atom economy
8. Use safer solvents and reaction conditions
9. Increase energy efficiency
10. Design for degradation
11. Continous monitoring/control to prevent pollution
12. Minimise potential for accidents

Front 9

Explain 'Avoid chemical derivatives'

Back 9

Avoid using blocking or protecting groups and temporary modifications. Derivatives use additional reagents and generate waste!

Front 10

How can we increase energy efficiency?

Back 10

Run reactions at room temperature and pressure, harness heat energy generated.

Front 11

How to work out atom economy:

Back 11

% atom economy
= ( sum of molar mass of used atoms ÷ sum of molar mass all reactants) x 100

Front 12

How nitrogen(IV) oxide is formed:

Back 12

in industrial and car emissions
2NO + O2 --> 2NO2
(NO = nitrogen(II) oxide)

Front 13

What forms acid rain?

Back 13

Acidic oxides of sulfur and nitrogen

Front 14

How sulfur dioxide and sulfur trioxide form sulfurous acid and sulfuric acid (which then dissociate):

Back 14

SO2 + H2O -> H2SO3 <--> H+ + HSO3-

SO3 + H2O --> H2SO4 --> H+ + HSO4-

Front 15

1. Nitrogen(II) oxide reacts in air to form brown poisonous gas nitrogen(IV) oxide:
^part of smog

2. Nitrogen(IV) oxide dissolves in rain water to form nitric and nitrous acid.

Back 15

1. 2NO + H2O --> 2NO2

2. 2NO2 + H2O --> HNO3 + HNO2

Front 16

What happens to limestome and marble in presence of acid rain (sulphuric acid):

Back 16

CaCO3 + H2SO4 --> CaSO4 + CO2 + H2O

Front 17

Primary pollutants in photochemical smog:

Back 17

sulfur dioxide, carbon monoxide, unburnt hydrocarbons, nitrogen(II) oxide (NO)

Front 18

Secondary pollutants in photochemical smog:

Back 18

Ozone, aldehydes, PAN, etc.

Front 19

Preparing oxygen in the lab:

Back 19

MnO2
2H2O2 ----> 2H2O + O2

Front 20

Test for carbon dioxide:

Back 20

CO2 + Ca(OH)2 --> CaCO3 + H2O

Front 21

Heating limestone (calcium carbonate) to get carbon dioxide:

Back 21

CaCO3 --> CaO + CO2

Front 22

Lab prep of carbon dioxide

Back 22

CaCO3 + 2HCl --> CaCl2 (aq) + CO2 +H2O