C6 module

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Acids and Alkalis and Neutralisation

pH scale = measures acidity or alkalinity across a 14 point scale

Acids = pH less than 7 Alkali = pH greater than 7

Acidic compounds = produce aqueous hydrogen ions when dissolved in water

Alkali compounds = produce aqueous hydroxide ions when dissolved in water

Acid + base = neutral salt solution + water

Neutralisation = remaining solution has neutral pH of 7

Hydrogen ions from the acid react with hydroxide ions from the alkali to make water

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Making Salts

Acid + metal hydroxide = salt + water

Acid + metal oxide = salt + water

Acid + metal carbonate = salt + water + carbon dioxide

Acid + metal = salt hydrogen

Hydrochloric acid = chloride salts

Sulfuric acid = sulphate salts

Nitric acid = nitrate salts

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Calculating products and reactants

Reactants = substances present before chemical reactions take place

Products = new substances made at the end of chemicals reaction

Yield = amount of product obtained from a chemical reaction

Percentage yield compares...

- actual yield

- theoretical yield

Relative atomic mass = mass of one atom in comparison to mass of other atoms

Relative formula mass = relative atomic mass of all the elements added together

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Chemical reactions

Chemical synthesis =

process by which raw materials are made into useful products. Need to consider economic and safety factors when carrying it out on an industrial scale

Titration =

calculates the concentration of an acid by finding out how much alkali is needed to neutralise it.

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Rates of Reaction

Rate of reaction = amount of reaction that takes place in given amount of time

Can be found by...

- weighing reaction mixture

- measuring volume of gas produced

- observing formation of precipitate

Affected by...

- temperature

- concentration

- surface area

- catalysts

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Rates of Reaction

Cold reaction mixture = particles collide less often

Hot reaction mixture = particles collide more often

Low concentration mixture = particles collide less often

High concentration mixture = particles collide more often

Large particles = fewer successful collisions

Small particles = more successful collisions

Collision theory = chemical reactions only occur when particles collide with each other with sufficient energy

Catalyst = increases rate of reaction without being used up

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