National Chemistry

 

This page contains information which is essential to success in the exam.

 

1.   Define and recognise examples of :-

isotopes           isomers               catalyst           electrolysis        neutralisation           precipitation        redox            unsaturated

hydrolysis        condensation      addition          homologous series       

 

 

2. Learn about the following

Bonding in:-                                       (a) metals               (b) ionic compounds      (c) covalent substances

Conductivity of:-                                 (a)  metals ionic    (b) compounds                (c) covalent substances

 

low melting point = covalent molecule

 

 tetrahedral shape  eg   CCl4        SiH4         CH4            (beware    NH3   )

 

3. Electronic configuration of atom and ion.

What caused the change ?

 

4. Write ionic formula zinc nitrate iron(II) oxide calcium hydroxide

Write ionic formulae for  aluminium sulphide, potassium oxide, magnesium chloride and iron(III) bromide

See how to write formula using the complex (polyatomic)  ions found on page 4

 

5. Copy out and/or recognise oxidation and reduction - redox - use page 7 of the data book

for  reactions, cells and electrolysis

 

6. Calculate given two figures the third using

 

                                   mole = mass in question                                            concentration =  mole

                                                mass of 1 mole                                                                        litres

 

7.  Non-metal oxide = acidic = Hydrogen ion = low pH  (high acidity low pH !!) ; turns indicator red

              metal oxide = alkali = hydroxide ion  = high pH (NB         alkali metals); turns indicator blue

                                 pH 7 is  neutral where hydrogen ions = hydroxide ions

 

 

8.                     Acid + metal oxide            ----> water + salt

                        Acid + metal hydroxide     ----> water + salt

                        Acid + metal carbonate    ----> water + salt + carbon dioxide

                        Acid +(reactive) metal       ----> hydrogen + salt (also redox)

pH moves to 7 (increases); H+ decreases = neutralisation

 

9. Electrochemical series - always happens to most reactive metal

                    most reactive oxidises faster

                     most reactive loses electrons to less active;

                     most reactive displaces less active

   

                    in a cell electrons flow from more reactive to less reactive

                    further aprt the metals in the electrochemical series (page 7) the greater the voltage

 

                     react fast break down slow

                     the morer reactive a metal the harder it is to extract from a compound with the most reactive metals needing  electrolysis to obtain the metal

                    A mid reactive metal such as iron is obtained by heating the oxide with carbon (a reducing agent - steals the oxygen) in a blast furnace

 

10. Draw alkane and alkene with two to six carbons

bromine water decolourises by alkenes

fractional distillation based on melting points

properties- viscosity, Boil pt, ignition temp., density, increase with size/mass

cracking produces smaller molecules one of which is an alkene

 

 

11. Corrosion requires water and oxygen

Iron (Fe) rusts to iron (II) ions (Fe2+) which turn ferroxyl indicator blue

appearance of the blue colour means oxidation (loss of electrons) of iron>

Iron (II) ions (Fe2+) oxidise further to iron (III) ions (Fe3+)

 

12. More reactive metal (eg Mg, Zn) sacrificially protects iron

Coating with zinc called galvanising

Iron corrodes to protect less reactive metal (eg Sn)

 

13. Calculate empirical formula

Calculate percentage composition

 

14. Alkene monomers react by addition (breaking one of the bonds in the C=C)

to polymerise (watch)

                            monomer                            polymer             repeating unit

 

15. Plastics

advantages - light, durable, insulator,

disadvantages - do not rot (durable), burn to give poisonous fumes

Themosetting- not softened by heat;

thermoplastic</STRONG> softened by heat

 

16. Fertilisers required to produce sufficient food.

Natural Bacteria methods cheaper

nitrogen is an unreactive gas - needs lot of energy to react with oxygen

Haber (Iron catalyst) process reacts nitrogen and hydrogen to make ammonia - high pressure (expensive) moderately high temperature

moderately high temperature = low yield of ammonia but faster reaction

Oswald (platinum catalyst) process ammonia to produce nitrogen dioxide to make nitric acid - high temperature to start with then as exothermic supplies own heat

HI=Haber & Iron; OP=Oswald & platinium

 

17. Substances with Carbon burn to give CO2

Substances with Hydrogen burn to give H2O

Substances - Hydrocarbons and carbohydrates - that burn to give CO2  and H2O must contain H and C (but could contain other elements).

>Carbohydrates produced by photosynthesis also produces oxygen

respiration in animals use carbohydrates

 

18. Carbohydrates

                Fructose    C6H12O6      monosaccharide       turns hot blue Benedict's brick red          

                Glucose     C6H12O6      monosaccharide       turns hot blue Benedict's brick red      

 

                Maltose     C12H22O11      disaccharide            turns hot blue Benedict's brick red      

                Sucrose    C12H22O11      disaccharide            no test

     

                Starch        (C6H10O5)n    poloysaccharidde   turns iodine blue-black

 

 

 

Isomers have same molecular formula but different structural formula

 

19. Glucose molecules joining together to form starch and water is condensation polymerisation

Starch or sucrose molecules being broken down by water is hydrolysis reaction.

Small glucose molecules can pass through the gut wall.

Hydrolysis occurs in body using biological catalysts called enzymes

Enzymes used in fermentation to produce (ethanol) a member of the alcohol homologous series.

 

20. Gases

Noble gases (He, Ne, Ar etc) do not react - monatomic - full outer orbital

Diatomic gases - elements O2, H2, Cl2, F2, N2

                              - compounds CO, HCl

Air - 80% nitrogen and 20% oxygen

Metal oxides (eg alkali metals) produce alkalis and

ammonia NH3 is only alkaline gas

Non-metal oxides C02, N02, SO2 produce acids

 

CO2 produced by heating carbonate or reacting an acid + carbonate;

turns lime water milky; used in photosynthesis

 

H2 released when metals (not copper or unreactive metal) react with acid

or when very reactive metals react with water;

produced when acid electrolysed;

 burns with a pop

 

O2 relights glowing splint;    produced by photosynthesis;    used in combustion

 

CH4 natural/North Sea gas; burns to give C02 and H2O;  has tetrahedral shape;

 

NH3 alkaline gas; produced when sodium hydroxide reacts with ammonium compound

 

Making gases

acid + metal (not Cu. Ag etc) ---> H2

acid + carbonate ---> CO2

alkali + ammonium ---> NH3