INORGANIC - GROUP 2

Question 1

describe the trend in atomic radius

Answer 1

atomic radius increases down the group
this is because the atoms have more shells of electrons making the atom bigger

Question 2

describe the trend in melting points

Answer 2

Decreases
weaker metallic bonding as the atomic size increases - the distance between the positive ions and delocalised electrons also increases
Therefore the electrostatic forces between the positive ions and delocalised electrons weakens
- magnesium is an exception from this rule as its crystals can’t pack as closely together

Question 3

Trend in 1st ionisation energy

Answer 3

DECREASES
outermost electrons are held more weakly as they are successively further from the nucleus
the outer shell electrons are more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons

Question 4

magnesium and steam reaction

Answer 4

reacts to produce magnesium oxide and hydrogen
Mg would burn with a bright white flame - MgO appears as a white powder
Mg + H2O —> MgO + H2

Question 5

magnesium and water reaction

Answer 5

produces magnesium hydroxide
slower reaction than steam as there is no flame
Mg + 2H2O —-> Mg(OH)2 + H2

Question 6

Other reaction with water

Answer 6

react to form hydroxides
Ca + 2H2O —> Ca(OH)2 + H2
Sr + 2H2O —> Sr(OH)2 + H2
Ba + 2H2O —> Ba(OH)2 + H2

Question 7

observations with water

Answer 7

fizzing, (more vigorous down group)
the metal dissolving, (faster down group)
the solution heating up (more down group)
with calcium a white precipitate appearing
(less precipitate forms down group with
other metals)

Question 8

What is titanium used for

Answer 8

making strong, light alloys for use in airfact

Question 9

Why is magnesium used to extract titanium

Answer 9

as it is more reactive metal than titanium
- titanium cannot be extracted with carbon as TIC is formed
- no electrolysis has it has to be very pure

Question 10

Steps in extracting titanium

Answer 10

1. TiO2 (solid) is converted to TiCl4
   (liquid) at 900C:
2. The TiCl4 is purified by fractional distillation in an argon
   atmosphere.
3. The Ti is extracted by Mg in an argon atmosphere at 500C

Question 11

Why is titanium extraction expensive

Answer 11

1. Mg is expensive
2. Batch process expensive as process is slower
3. High temps required

Question 12

Mg and Ti equation

Answer 12

TiO2 + 2 Cl2 + 2 C —–> TiCl4 + 2 CO
TiCl4 + 2Mg —-> Ti + 2 MgCl2

Question 13

Trend in solubility of hydroxides

Answer 13

more soluble down the group
if its insoluble then white precipitates will be formed

Question 14

Magnesium hydroxide solubility

Answer 14

classed as insoluble in water
simplest ionic equation =
– Mg2+(aq) + 2OH-(aq) —> Mg(OH)2 (s).
magnesium hydroxide in water will
appear slightly alkaline (pH 9) so some hydroxide ions must therefore have been produced by a very slight dissolving and therefore it can be classed as sparingly soluble

Question 15

How is magnesium hydroxide used in medicine

Answer 15

to neutralise excess acid in the stomach and to treat constipation
- Mg(OH)2 + 2HCl —-> MgCl2 + 2H2O
it is so weakly alkaline. It is
preferable to using calcium carbonate as it will not
produce carbon dioxide gas.

Question 16

Calcium hydroxide solubility

Answer 16

Classed as partially soluble in water and will appear as a white precipitate
Used in agriculture to neturalise acidic soils
Aqueous solution of CaOH is called lime water and can be used to test for CO2
Ca(OH)2 (aq) + CO2 (g) —> CaCO3 (s) + H2O(l)

Question 17

Barium hydroxide solubility

Answer 17

Easily dissolve in water
Hydroxide ions present make the solution strongly alkaline
Ba(OH)2(s) + aq —> Ba2+ (aq) + 2OH-(aq)

Question 18

What is the least soluble sulfate

Answer 18

BaSO4

Question 19

BaSO4 use in medicine

Answer 19

used as a barium metal and is given to patients who need x-rays of their intestine
barium absorbs the x-ray and so the gut shows up on the x-ray image

Question 20

testing for presence of a sulfate ion

Answer 20

BaCl2 solution acidified with hydrochloric acid is used as a reagent to test for sulfate ions
The hydrochloric acid is needed to react with carbonate impurities that are often found in salts which
would form a white barium carbonate precipitate and so give a false result. You could not use sulfuric acid
because it contains sulfate ions and so would give a false positive result
If acidified barium chloride is added to a solution that contains sulfate ions a
white precipitate of barium