Hypothesis - I am going to be examining how much energy is transferred as heat when acids react with alkalis, also known as the heat of neutralisation.

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Fatima Memon

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In this Investigation I am going to be examining how much energy is transferred as heat when acids react with alkalis, also known as the heat of neutralisation.

What are acids?

Substances with a pH of less than 7 are acids. The stronger the acid, the lower the pH number. Acids turn blue litmus paper red. They turn universal indicator red if they are strong, and orange or yellow if they are weak. It also produces H+ ions in water.

 Examples of acids  

  • Magnesium chloride
  • Nitric acid
  • Hydrochloric acid
  • Sulphuric acid
  • Potassium carbonate
  • Sulphurous acid
  • Citric acid

What are alkalis?

An alkali is a base that is soluble in water. An alkali is a basic, ionic salt of an alkali metal or alkali earth metal element.
Alkalis are best known for being bases (compounds with pH greater than 7) that dissolve in water.

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Examples of alkalis

  • Sodium hydroxide  - NaOH
  • Calcium hydroxide  - Ca(OH)2
  • Potassium hydroxide - KOH

Neutralisation

When an alkali is added to an acid, the pH of the mixture rises as the alkali reacts with it forming neutral products. An acid added to an alkali causes the pH to fall because the alkali is removed by reaction with the acid.

A reaction in which acidity or alkalinity is removed is called neutralisation. A neutralisation involving an acid and a base (or alkali) always produces salt and water (and nothing else).

Acid + base  salt ...

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