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CHEMICAL EQUATIONS (Acid with metals (ALL acids contain hydrogen, Metals…
CHEMICAL EQUATIONS
Acid with metals
ALL acids contain hydrogen
Metals that are more reactive than hydrogen can displace it
Acid + Metal ---- Salt + Hydrogen
Mg reacts rapidly, Zinc reacts quite rapidly, Iron reacts fairly slowly.
Extraction of metals
unreactive metals are found in the earth
A more reactive element will displace a less reactive element from its compound
certain metals can be extracted with carbon
3 reactions of acids
Acid + base --- salt +water
Acid + metal --- salt + water
Acid + metal carbonate --- salt + water + carbon dioxide
Strong and weak acids
Strong acids fully ionise in aqueous solutions, but weak acids partially ionise
weak acids - carbonic acid, ethanoic acid, citric acid
As the Ph decreases by 1, the amount of H+ ions decreases by 10
Electrolysis of aqueous solutions
Aqueous solutions are dissolved in water and water molecules ionise to form hydrogen and hydroxide ions
Hydrogen is produced at the cathode if the metal is more reactive than hydrogen
e.g. Copper - copper is less reactive than hydrogen so copper is produced at the cathode. At the anode, oxygen gas is made and platinum is often used as the inert electrodes.
Reaction of metals with O2
When a metal reacts with oxygen, it forms a metal oxide
Gaining oxygen is an oxidation reaction, the loss of oxygen is a reduction reaction
Oxidation and reduction in electrons
Oxidation is loss of electrons, reduction is gain
Oxidation + Reduction -
Acids and alkalis
Acids produce H+ ions in aqueous solutions
Bases - chemicals that neutralise acids an produce salts and water
Bases that are soluble are alkalis
Acid with metals 2
Acids produce H+ ions in aqueous solutions
Rate of reaction with dilute acids : Mg is very rapid, Zinc is quite rapid, Iron is very slow
Titration calculations
Moles (mol) = concentration (mol/dm3) x volume (dm3)
Known concentration in only 1 solution = Work out the number of moles in the 1 solution, work out the amount of moles in the other solution, use the equation to work out concentration
Electrolysis intro
solid ionic compounds CANNOT conduct electricity, the ions are not free to move
Electrolysis is when ionic substances are decomposed when an electric current passes through them. These substances must be free to move, so they are dissolved first.
Electrolysis of aluminium oxide
Aluminium is extracted from aluminium oxide using electroysis
Aluminium oxide contains the aluminium ion and oxide ion and this has a very high melting point. It is first mixed with cyolite to lower the melting point. the cathode and anode are both made of graphite. the aluminium ions are attracted to the cathode and each ion gains 3 electrons. the oxide ions are attracted to the anode and each ion loses 2 electrons. Carbon dioxide is produced.
Reactivity series
Most to least : potassium, sodium, calcium, magnesium, aluminium, (carbon),zinc, iron ,tin, lead, (hydrogen), copper, silver, gold, platinum
Electrolysis of aqueous solutions 2
e.g. sodium chloride solution - If the solution contains halide ions, then halogen will be produced at the anode. At the anode, chlorine gas is produced.
Cathode = 2H+ + 2e- ----- H2
Anode = Cl- ---- Cl + e-
The anode of a device is the terminal where current flows in from outside. The cathode of a device is the terminal where current flows out.
