Chemistry Revision

Catalytic convertors

The catalytic convertors are a honeycomb structure, made of a ceramic material coated with platinum and rhodium metals which are the catalysts. The honeycomb provides a large surface area for the reaction to take place.

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Zeolites

These are minerals that have a very open pore structure that ions or molecules can fit into.

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Group 2 (alkaline earth metals)

These are called alkaline earth metals because their oxides/hydroxides are alkaline. They are s-block elements that get more reactive as you go down the group however they are less reactive then Group 1 despite sharing similar properties

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Electron arrangement/ionisation energy

The elements all have two electrons in an outer s-orbital. In all their reactions, atoms of elements lose their two outer electrons to form ions with a 2+ positive charge.

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why does ionisation energy decrease down the group?

The ionisation energy decreases down the group because the electrons become further away from the positive nucleus as the nucleus has more shielding due to more inner levels os shells filled

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why does the size of the atoms increase down the group?

The s-orbital gets further from the nucleus as there are more inner levels filled-more shielding hence the atomic radii increases

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Melting points

Group 2 elements are metals with high melting points, as you go down the group the sea of delocalised electrons gets further from the positive nucleus hence the strength of the metallic bonds decrease

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Magnesium's melting point

Magnesium is an exception of the trend of the decrease in melting points down the group due to it's different lattice arrangement. Therefore magnesium has the lowest melting point

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Group 2 reacting with water

the metals get more reactive down the group when added with water. These are redox reactions

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When will magnesium/other metals in group 2 react quickly/slowly and with what?

Magnesium/other group 2 metals react more vigorously with steam and are slower when reacting with cold water

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What is the reaction for magnesium with cold water?

Mg(s) + 2H2O(l) = Mg(OH)2(aq) + H2(g)

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What is the reaction for magnesium with steam?

Mg(s) + H2O(g) = MgO(s) + H2 (g)

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What is Magnesium hydroxide/ 'milk of magnesia' used for and why is this possible?

Magnesium hydroxide is used for indigestion remedies to neutralise excess stomach acid. It is possible for magnesium hydroxide to be up taken without causing harm because it is insoluble.

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What is calcium hydroxide sometimes called and what does it do?

Calcium hydroxide is often called 'Slaked lime' and treats acidic soil. Most plants have an optimum level of acidity or alkalinity e.g. crops such as wheat and corn prefer soil that is neutral

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solubilities of metals with hydroxides and sulfates?

Metal hydroxides become more soluble down the group whereas metal sulphates become less soluble going down the group

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Hydroxides

These are all white solids-Mg(OH)2 is so insoluble hence sold as suspension in water up to Ba(OH)2 which is very soluble and dissolves to produce strong alkaline solution: Ba(oh)2 (s) + aq = Ba2+(aq) + 20H- (aq)

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what does barium sulfate do and what can it be called? why is it not harmful?

Barium sulfate can be called 'Barium meal' which can be taken by mouth, it outlines the gut in x-rays, it can also test for sulfate ions. It can be taken by mouth without causing harm because it is virtually insoluble

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What happens when you test for sulfate ions using barium chloride?

The solution is acidified with hydrochloric acid and then barium chloride solution is added. if a sulfate is present a white precipitate of barium sulfate is formed.The addition of acid removes carbonate ions as carbon dioxide.

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Equation for identifying sulfate ions using barium chloride

Ba2+(aq) + SO4 2- (aq) = BaSO4(s)

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