Acids

pH and Indicators

Universal Indicator

• 
• Acidic - less than 7
• Neutral - 7
• Alkaline - more than 7

Litmus

• 
• Acidic - red
• Neutral - purple
• Alkaline - blue

Methyl Orange

• 
• Acidic - red
• Neutral - orange
• Alkaline - yellow

Phenolphthalein

• 
• Acidic - colourless
• Neutral - milky white
• Alkaline - pink/purple

Summary Equation - Metals above H2

• metal + acid --> salt + hydrogen
• Salts:
• Sulphuric acid - sulphates
• Hydrochloric acid - chlorides
• Nitric acid - nitrates

Making Hydrogen in the Lab

• zinc and dilute sulphuric acid with very small amount of CuSO4, in which the copper that is produced acts as the catalyst.
• Hydrogen reacts with oxygen in presence of flame or spark to give water and gives squeaky pop with lighted splint placed at mouth of test tube.
• 2H2(g) + O2(g) --> 2H2O(l)
• 

Bases

• Substances that combine with hydrogen ions.
• Bases soluble in water are called alkali.
• Bases at GCSE:
• - Metal oxides (containing oxide ions)
• - Metal hydroxides (containing hydroxide ions)
• - Metal carbonates (containing carbonate ions)
• - Ammonia
• All have ability to combine with hydrogen.

Reacting Acids with Metal Oxides

• metal oxide + acid --> salt + water
• Neutralisation Reactions:
• When an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. The neutralisation of a strong acid and strong base has a pH equal to 7.

Reacting Acids w Metal Hydroxides

• metal hydroxide + acid --> salt + water

Reacting Acids with Carbonates

• Carbonates react with cold dilute acids to produce CO2 gas.
• carbonate + acid --> salt + carbon dioxide + water

Hydrogen chloride and HCL acid

• Hydrogen chloride - gas, hydrochloric acid - aqueous solution
• When hydrogen chloride dissolves in water - gives hydroxomonium and chloride ions
• The hydroxomonium ions give hydrochloric acid its simple acidic properties - with litmus, metals, carbonates, etc.
• Hydrogen chloride dissolved in methylbenzene won’t show simple acidic properties of hydrochloric acid provided no trace of water present
• Won’t turn blue litmus paper red (provided paper perfectly dry)
• Won’t react with magnesium ribbon to produce O2
• Won’t react with calcium carbonate in the form of marble chips to produce CO2
• If water present, hydrogen chloride reacts with it, and simple acidic properties restored since HCl reacts to form ions, especially hydroxomonium ion.