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a level chemistry > Group 2 Metals > Flashcards

Group 2 Metals Flashcards

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1
Q

What are group two metals also known as?

A

The alkaline earth metals.

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2
Q

What bonding occurs in G2?

A

Metallic.

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3
Q

Starting from Be list G2 to Ra.

A

Be, Mg, Ca, Sr, Ba, Ra.

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4
Q

Trend of atomic radius down G2?

A

Increases.

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5
Q

Why does atomic radius change down G2?

A

More principal energy levels are occupied. These levels are further from the nucleus and additional shells shield the outer e-s from the nuclear charge. The outer e-s are attracted less strongly the further from the nucleus they are.

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6
Q

Trend of 1st ionisation energy down G2?

A

Decreases.

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7
Q

Why does the 1st ionisation energy change down G2?

A

Outer e- is removed more and more easily, e- is removed from a successively higher principal energy level further from the nucleus. More shielding/ no. of energy levels between the outer shell and the nucleus. Extra inner e-s shield the outer e-s from the increased nuclear charge so less energy is needed to remove it.

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8
Q

Trend of m.p and b.p down G2?

A

Decreases.

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9
Q

Why does m.p and b.p change down G2?

A

All metallically bond and each atom gives 2 e-s into the structure, the attraction between the + ion and - e-s hold the metal together, the stronger the attraction the higher the m.p. The + ions get bigger down the group and the extra shells of e-s shield the attraction of the metal ion nuclei and the free e-s. Metallic bonds get easier to break and m.p is lower.

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10
Q

What element is the exception to the m.p trend in G2?

A

Mg.

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11
Q

Why is Mg lower m.p?

A

Has a different metallic structure.

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12
Q

How does Mg react with water?

A

Reacts very slowly with cold water, readily with steam.

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13
Q

Equation for Mg and water?

A

Mg(s) + H2O(g) -> MgO(s) + H2(g).

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14
Q

How does Ca react with water?

A

Reacts with cold water.

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15
Q

Equation for Ca and water?

A

Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g).

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16
Q

How does Sr react with water?

A

Reacts quickly with water.

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16
Q

What is the equation for Sr and water?

A

Sr(s) + 2H2O(l) -> Sr(OH)2(aq) + H2(g).

17
Q

How does Ba react with water?

A

Reacts very quickly with cold water.

18
Q

Equation for Ba and water?

A

Ba(s) + 2H2O(l) -> Ba(OH)2(aq) + H2(g).

19
Q

What is the trend in reactivity with water down G2?

A

Increase in reactivity.

20
Q

Explain the trend in G2 reactivity with water.

A

Down the group the outer e-s are further from the nucleus and are lost more easily making the element more reactive. There is more shielding of the outer e-s as we go down the group.

21
Q

Define solubility.

A

Dissolves in water.

22
Q

Define insolubility.

A

Doesn’t dissolve in water.

23
Q

As we go down the group how does reactivity of hydroxides change?

A

Increases.

24
Q

As we go down the group how does reactivity of sulphates change?

A

Decreases.

25
Q

How soluble is Mg(OH)2?

A

Sparingly.

26
Q

What is magnesium hydroxide used for?

A

Laxatives, medicine for digestive upset.

27
Q

What is calcium hydroxide used for?

A

In agriculture to neutralise acidic soil.

28
Q

What is calcium oxide or calcium carbonate used for?

A

Remove sulphur dioxide from flue gases in a chimney. Line the chimney with it and it reacts with the sulphur dioxide. They are both bases, this is a neutralisation reaction.

29
Q

How soluble is BaSO4?

A

Insoluble.

30
Q

What is barium sulphate used for?

A

Barium meal is given to patients when X rays of the digestive system are needed. It can be used in medicine as it’s insoluble and isn’t absorbed.

31
Q

What is magnesium used for?

A

Extract titanium from titanium chloride in industry to get titanium metal. Displacement reaction, Mg is more reactive than Ti.

32
Q

Displacement equation for Mg and Ti?

A

2Mg + TiCl4 -> 2MgCl2 + Ti.

33
Q

What do we do to test for sulphate ions?

A

Add 1cm^3 of dilute HCl to solution being tested. Add 1cm^3 of dilute barium chloride to test tube.

34
Q

If sulphate ions are present what result occurs?

A

A white precipitate of barium sulphate is formed.

35
Q

Why do we add acid to the solution in the sulphate test?

A

To remove any other ions that would also give a precipitate.

36
Q

What other ions would give a precipitate if not removed by acid?

A

Carbonate ions, CO3^2-.

37
Q

Why don’t we use sulphuric acid in our sulphate ions test?

A

It contains sulphate ions that would also give a white precipitate.

38
Q

How do we calc. % mass?

A

Moles of one you know, mass of other reactant, difference in masses, do percentage over whole mass of reactants.

39
Q

Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water.

A

Ca(s) + 2H2O(l) -> Ca2+(aq) + 2OH-(aq) + H2(g)

40
Q

Write an equation for the thermal decomposition of zinc carbonate to zinc oxide.

A

ZnCO3 -> ZnO + CO2

41
Q

How do you do % atom economy?

A

New comp/ old comp x 100

a level chemistry (26 decks)

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