C2: Acids, Alkalis and Salts

Here is a set of revision cards for students taking AQA Additional Science. These cards are based on Acids, Alkalis and Salts from the C2 (Chemistry) section. I hope these help you to revise! Please rate and comment on how to improve :) Also, I have a study group called AQA Additional Science where we discuss topics such as this one and more. Feel free to become a member, the more the merrier!

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  • Created by: I P B
  • Created on: 21-12-09 15:06

Key Words and Definitions

Acid = a compound that has a pH value of lower than 7

Alkali = a compound that has a pH value of higher than 7

Neutralisation = a reaction between an acid and a base which forms a neutral solution

Precipitation = the removal of particles from a solution

Salt = the product of a chemical reaction between a base and an acid

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Key Words and Definitions Continued...

Soluble = a substance that can be dissolved (most commonly in water)

Insoluble = a substance that can not be dissolved i.e. cannot form a solution e.g. sand and water do not form a solution so sand is insoluble

Bases = chemicals which can neutralise acids

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All acids form H+ (hydrogen) ions when added to water

It is the hydrogen ions that make a solution acidic

the (aq) symbol shows that the ions are dissolved in an aqueous solution

The three acids you must know are Hydrochloric acid (HCl), Nitric acid (HNO3) and Sulphuric acid (H2SO4)

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All alkalis are bases

Bases are the opposite to acids in the way they react

They dissolve in water (which is why they are used most commonly)

All alkalis form hydroxide ions (OH-) when added to water

It is the hydroxide ions which make a solution alkaline

Metal oxides and hydroxides are bases too. The soluble hydroxides are called alkalis.

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pH Scale

Indicators are special chemicals which change colour when they are added to acids or alkalis e.g. litmus paper

Universal Indicator can show a variety of colours to give an accurate pH:

red = very acidic

orange/yellow = weak acid

green = neutral

blue = weak alkali

purple = very alkaline

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Insoluble Salts

Insoluble Salts are made by mixing appropriate solutions of ions so that a precipitate is formed

Precipitation can be used to remove unwanted ions from solutions

This technique is used in treating water for drinking, softening hard water. The calcium or magnesium are removed as insoluble calcium/magnesium carbonate.

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Acids and Alkalis are chemical opposites, so if added together in equal amounts, they cancel eachother out

The hydrogen ions (H+) from the acid react with the hydroxide ions (OH-) from the alkali to produce water

The pH of water is 7 meaning that water is neutral

H+ (aq) + OH- (aq) > H2O (l)

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Soluble Salts

Soluble salts can be made from acids by reacting them with:

  • metals - not all metals are suitable, some are too reactive and some others are not reacitve enough
  • insoluble bases - the base is added to the acid until no more will react and the excess solid is filtered off. crystals can be produced if the water is evaporated
  • alkalis - an indicator can be used to show when the acid and alkali have completely reacted to produce a salt solution

Salt Solutions can be crystallised to produce salt

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Equations To Remember

Acid + Alkaline Hydroxide Solution > Neutral Salt Solution + Water

Acid+ Metal > Salt + Hydrogen

Acid + Base > Neutral Salt Solution + Water

Acid + Alkaline Hydroxide Solution > Neutral Salt Solution + Water

Acid + Metal Oxide > Salt + Water

Acid + Metal Hydroxide > Salt + Water

Acid + Metal Carbonate > Salt + Water + Carbon Dioxide

Solution (aq) + Solution (aq) > Precipitate (s) + Solution (aq)

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Naming Salts

The first part of the name comes form the metal in the base or carbonate. The second part comes from the acid used


Sodium hydroxide + Hydrochloric acid > Sodium Chloride + Water

Zinc oxide + Sulphuric acid > Zinc Sulfate + Water

Hydrochloric acid produces chlorides

Nitric acid produces Nitrates

Sulphuric acid produces Sulphates

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Common Case Study - Example

Ammonia dissolves in water to produce an alkaline solution

It is used to produce ammonium salts

Ammonium Salts are important as fertilisers

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John wrote:


LOL Thankyou! I find this topic really hard so I did LOTS of work on it to compensate :D



Really helpful, I totally get this stuff. (:



Thank you

Really helped me learn this-not revise as it's new to me ;)



thankyouu this has really helped me :)

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