Additional Science - Chemistry Checklist (Page 2 of 2) in pdf

released from forming new bonds

Catalysts provide a different pathway for a chemical reaction that has a lower activation energy

Hydrogen can be burned as a fuel in combustion engines. It can also be used in fuel cells that produce

electricity to power vehicles. Hydrogen + Oxygen $ Water

Flame tests identify metal ions. lithium $ crimson, sodium compounds $ yellow, potassium compounds $

lilac, calcium compounds $ red, barium compounds$ green

Aluminium, calcium & magnesium ions form white precipitates with sodium hydroxide solution but only the

aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution

Copper(II), iron(II) & iron(III) ions form coloured precipitates with sodium hydroxide solution. Copper forms

a blue precipitate, iron(II) a green precipitate & iron(III) a brown precipitate

Carbonates react with dilute acids to form carbon dioxide. Carbon dioxide produces a white precipitate with

limewater. This turns limewater cloudy

Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid.

Silver chloride is white, silver bromide is cream & silver iodide is yellow

Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute

hydrochloric acid

The volumes of acid & alkali solutions that react with each other can be measured by titration using a

suitable indicator

HT: If the concentration of one of the reactants is known, the results of a titration can be used to find

the concentration of the other reactant

The raw materials for the Haber process are nitrogen & hydrogen. Nitrogen is obtained from the air &

hydrogen may be obtained from natural gas or other sources

The purified gases are passed over a catalyst of iron at a high temperature & a high pressure Some hydrogen

& nitrogen reacts to form ammonia. The reaction is reversible. Remaining hydrogen & nitrogen are recycled

HT: When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions

occur at exactly the same rate in each direction. Relative amounts of reacting substances at

equilibrium depend on the conditions of the reaction

HT: If the temperature is raised, the yield from the endothermic reaction increases & the yield from the

exothermic reaction decreases

HT: If the temperature is lowered, the yield from the endothermic reaction decreases & the yield from

the exothermic reaction increases

HT: In gaseous reactions, an increase in pressure will favour the reaction that produces the least

number of molecules as shown by the symbol equation for that reaction

HT: These factors, together with reaction rates are important when determining the optimum

conditions in industrial processes, including the Haber process

Alcohols contain the functional group –OH. Methanol, ethanol & propanol are the first three members of a

homologous series of alcohols

Methanol, ethanol & propanol dissolve in water to form a neutral solution, react with sodium to produce

hydrogen, burn in air, are used as a fuels & solvents, & ethanol is the main alcohol in alcoholic drinks

Ethanol can be oxidised to ethanoic acid, either by chemical oxidising agents or by microbial action. Ethanoic

acid is the main acid in vinegar

Ethanoic acid is a member of the carboxylic acids, which have the functional group –COOH

HT: It does not ionise completely when dissolved in water & so is a weak acid. Aqueous solutions of

weak acids have a higher pH value than aqueous solutions of strong acids with the same concentration

Ethyl ethanoate is the ester produced from ethanol & ethanoic acid. Esters have the functional group –

COO–. They are volatile compounds with distinctive smells & are used as flavourings & perfumes

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