chemical changes

What is oxidation?

What is oxidation?

Loss of electrons, gain of oxygen

What is reduction?

gain of electrons, loss of oxygen

metals reactivity series in order of most reactivity to least

potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper

Which non-metals are often put into the reactivity series?

hydrogen and carbon

A more reactive metal will...

Displace a less reactive metal from its compound

ACRONYM for reactivity series

Please Stop Calling Me A Cute Zebra I Like Hearing Copper Silver Gold

most metals are found as

compounds that require chemical reactions to extract the metal

Metals less reactive than carbon

Can be extracted from their oxides by reduction with carbon

acids react with metals to produce

salt and hydrogen gas

What is a redox reaction?

an oxidation reaction paired with a reduction reaction

example of redox reaction

rusting

Acids and Bases

neutralize each other

Acid + Base

salt + water

Acid + metal carbonate

salt + water + carbon dioxide

How can soluble salts be made?

by reacting acids with insoluble bases such as metal oxides, metal hydroxides and metal carbonates

a) React the excess acid with some insoluble chemical (e.g. metal oxide) b) Filter off the leftovers c) Crystallise the product

strong acid

an acid that ionizes completely in aqueous solution (HCl)

weak acid

an acid that is only slightly ionized in aqueous solution (citric acid ethanoic acid)

What is an electrolyte?

a liquid containing free-moving ions which conducts electricity

what is electrolysis

The breaking down of a substance using electricity

positively charged ion

cation moves to negative electrode (cathode)

negatively charged ions move to

anion moves to anode (positive electrode)

what is an electrode

A solid that conducts electricity and is submerged in the electrolyte

When a simple ionic compound is electrolysed in the molten state using inert electrodes...

the metal is produced at the cathode and the non metal is at the anode

When is electrolysis used to extract metals

When the metal is more reactive than carbon OR if the metal reacts with carbon

Why must the anode be replaced regularly?

The anode must be replaced regularly because the oxygen produced at the anode reacts with the carbon in the graphite forming carbon dioxide gas

where is aluminium oxide found

bauxite

why is aluminium oxide hard to extract

because it has a high melting point and is found in bauxite

how can we prepare aluminium oxide for electrolysis

1- purify it 2- to make the ions free we need to make it molten so we mix it with cryolite which lowers the melting point

outcome of aluminium oxide electrolysis

negative oxygen ions move to the anode aluminium ions stay in the solution and can be extracted

rules for electrolysis of aqueous solutions at the cathode

•if it’s a metal more reactive than hydrogen then hydrogen is discharged •if it’s less reactive than hydrogen (eg copper) that will be discharged

rules for electrolysis at the anode

if it’s a halide (eg chloride, bromide, oxide) then it is discharged if it’s not a halide then hydroxide ions are discharged

what 2 ions are present in water

hydrogen and hydroxide

what is an aqueous solution

An aqueous solution is water that contains one or more dissolved substance eg salt water (nacl)

what is an ore

An ore is a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile

what do ionic equations show

the particles that change

what do half equations shiw

individual loss or gain of electrons for each atom

State the general equation for a neutralisation reaction in a short, ionic form.

H+ + OH- ———> H2O

As the pH is decreased by one unit, what change is seen in the hydrogen ion concentration?

increased by factor 10

What occurs at the cathode and what occurs at the anode during electrolysis?

reduction at cathode

oxidation and anode

In aqueous electrolysis, which element is discharged at the cathode? Oxygen is produced at the anode unless what?

The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal, in which case the said metal is produced. Oxygen is produced at the anode unless the solution contains halide ions, in which case halogen molecules are produced