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Reactivity tests + Extraction - Coggle Diagram
Reactivity tests + Extraction
REACTIONS OF REACTIVE METALS WITH WATER
Potassium, sodium and lithium all react quickly with cold water to produce a metal hydroxide and hydrogen gas
SODIUM
Sodium fizzes rapidly and melts to form a ball that moves around on the water surface.
LITHIUM
Lithium fizzes steadily and floats, becoming smaller until it eventually disappears.
POTASSIUM
Potassium is the most reactive so reacts very quickly.
The hydrogen produced ignites instantly and the metal also sets alight, sparking and burning with a lilac flame.
MAKING SOLUBLE SALTS
We can produce soluble salts through a reaction between acids and solid, insoluble substances such as pure metals, metal oxides, metal hydroxides, or metal carbonates.
Blue copper sulfate crystals are produced by adding black copper oxide to sulfuric acid:
CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)
REQUIRED PRACTICAL - SEPARATING METALS
The aim of this practical is to produce a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.
PREPARATION
1 - Use a Bunsen burner to gently warm the acid.
2 - Add the insoluble solid (with stirring) until the reaction no longer happens
FILTRATION
1 - Filter the solution to remove the excess insoluble solid.
This will leave a solution of the salt dissolved in water.
CRYSTALLISATION
1 - Heat the solution in an evaporating basin above a beaker of water.
The 'water bath' ensures gentle heating.
2 - Leave the solution to cool and allow more water to evaporate.
As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
THE PH SCALE
Strong acids have a pH close to 0
Acids form hydrogen (H+) ions when they dissolve in water.
pH less than 7 = acid.
pH more than 7 = alkali.
pH of exactly 7 = neutral.
Strong alkalis have a pH close to 14.
The acidity or alkalinity of a solution is measured using the pH scale, which ranges from 0 to 14.
Alkalis form hydroxide (OH-) ions when they dissolve in water.
ACIDS + ALKALIS
Acids and alkalis are on the opposite ends of the pH scale. They combine to form water, which is neutral.
ACIDS
Acids are substances that form hydrogen (H+) ions when they dissolve in water (aqueous solutions).
ALKALIS
Alkalis are substances that form hydroxide (OH-) ions when they dissolve in water (aqueous solutions).
An alkali is a type of base
MEASURED USING PH SCALE
The pH scale is used to measure how acidic or alkaline a substance is
OXIDATION + REDUCTION
Oxidation and reduction reactions are important types of reactions in chemistry.
OXIDATION
An oxidation reaction involves gaining oxygen.
It can also involve losing electrons.
E.g. when metals react with oxygen, metal oxides are produced:
Magnesium + oxygen → magnesium oxide
2Mg + O2 → 2MgO
REDUCTION
A reduction reaction involves losing oxygen.
It can also involve gaining electrons.
E.g. when metal oxides lose oxygen and return to their atomic form:
Iron oxide + carbon monoxide → iron + carbon dioxide
Fe2O3 + 3CO → 2Fe + 3CO2
REACTIONS OF METALS OF DILUTE ACIDS
Most metals react with dilute acids to give a salt (e.g. copper chloride) and hydrogen gas.
METALS THAT DO REACT WITH DILUTE ACIDS
Metals don't have to be that reactive to react with dilute acids
The metals that react with dilute acids but not cold water are magnesium, aluminium, zinc, iron and lead (iron and lead react slowly).
METALS THAT DON'T REACT WITH DILUTE ACIDS
The only metals that aren't reactive enough are copper, silver, gold and platinum.
EXTRACTION OF METALS
Most metals are only found as compounds because the metal has reacted with other elements in the past. Because of this, the metal has to be extracted from the ore (rock) where the metal compound is found.
WHY IS CARBON USED TO EXTRACT METALS?
Reducing a metal with carbon will result in the extraction of the metal if the metal is lower in the reactivity series than carbon.
Carbon is used because it is cheap and abundant.
HOW IS CARBON USED TO EXTRACT METALS?
In the reduction, the metal oxide loses oxygen to form a pure metal.
Reduction with carbon normally involves heating the metal oxide in the presence of the carbon, which is often used in the form of coal.
REACTIVITY SERIES
When reacting with other substances, metal atoms always form positive ions.
The reactivity of a metal is linked to how easy it is for a metal to form its positive ion.
Metals can be arranged in order of their reactivity.
Gold and platinum are examples of highly unreactive metals. These metals are found in the Earth’s crust as pure metals. We call them native metals.