Chemical change- Chemistry

A base neutralises an acid. Some examples of a soluble and insoluble base are Soluble base (alkali) e.g. Sodium hydroxid Insoluble base e.g. Zinc oxide

What is the neutralisation equation?  H + + OH -  H 2 O

Strong acid – fully ionised in solution e.g. nitric acid

Weak acid – partially ionised in solution e.g. ethanoic acid

PH SCALE

pH 1 – Red – Strong acid

pH 6 – Yellow – Weak acid

pH 7 – green – neutral

pH 8 – blue - weak alkali

pH 14 – purple – strong alkali

As the pH concentration decreases by one unit…….. The hydrogen ion concentration increases by a factor of 10

You can make copper sulfate crystals using an insoluble base and an acid:

Warm the acid

 Add copper oxide to excess

Filter the mixture

Warm the copper sulfate solution over a water bath til crystals first appear

Pour into a petri dish and leave to crystallise

Electrolysis – Using electricity to separate compounds

Cathode – Negative electrode

Anode – Positive electrode

Electrolyte - Compound is being separated into elements

In electrolysis, what always happens to the (movement and electrons):

Metal ions – Move to the negative electrode and gains electrons

Non-metal ions – Move to the positive electrode and lose electrons

Describe the process of extracting aluminium from aluminium oxide using electrolysis (think about the electrodes, electrolyte, half equations)

Dissolve aluminium oxide into cryolite

 Al 3+ + 3e -  Al

 2O 2- - 4e -  O 2

 Carbon electrodes wear away as the oxygen reacts with them to form carbon dioxide

the rules for the electrolysis of aqueous compounds are 

At the negative electrode – least reactive out of metal or hydrogen

 At the positive electrode – group 7 given out if not oxygen from hydroxide.

Oxidation is gain of oxygen

Reduction is loss of oxygen

OIL RIG Oxidation is loss of electrons

Reduction is gain of electrons

Potassium

Sodium

Lithium

Calcium

Magnesium

Zinc

Iron

Copper

one metal may be more reactive than another bacause It has a greater tendency to form positive ions.

Displacement reaction

More reactive metal replaces less reactive metal in compound

Magnesium + iron nitrate  magnesium nitrate + iron

How can metals be extracted from their

oxides? 

Unreactive metals e.g. gold found as the metal itself 

If below carbon in reactivity series – use carbon to displacethem from the oxide

If above carbon – use electrolysis

Acids – H + ions

Alkalis – OH - ions

soluble salts

Acid + metal  salt + hydrogen

Acid + alkali  salt + water

Acid + metal oxide  salt + water

Acid + carbonate  salt + water + carbon dioxide

What type of salt does each acid make?

Hydrochloric acid (HCl) - chloride

Sulfuric acid (H 2 SO 4 ) - sulfate

Nitric acid (HNO 3 ) - nitrate

metal reacting with an acid is a redox reaction because the metal is oxidised (loses electrons) to form a positive ions The hydrogen ion is reduced (gains electrons) to a hydrogen atom

Magnesium + hydrochloric acid  magnesium chloride

+ hydrogen

Mg + 2H +  Mg 2+ + H 2

Mg – 2e -  Mg 2+

2H + + 2e -  H 2

the end