Topic 4- Inorganic Chemistry And The Periodic Table

Question 1

Describe the trend in ionisation energy down group 2

Answer 1

• Nuclear charge increases
• Number of filled inner shells increases the level of repulsion
• Introduction of new quantum shell increases repulsion
• Increase in atomic radii

OVERALL: DECREASE

Question 2

What are the reasons for the trend in reactivity for Group 2 elements?

Answer 2

Reactivity increases down the group as the atomic radii increase there is more shielding. The nuclear attraction decreases and it is easier to remove (outer) electrons and so cations form more easily

Question 3

What are the reactions of Mg to Ba when reacted with oxygen?

Answer 3

2Mg + O2 -> 2MgO
2Ba + O2 -> 2BaO

Question 4

What are the reactions of group 2 elements between Mg to Ba when reacted with chlorine?

Answer 4

Mg + Cl2 -> MgCl2
Ba + Cl2 -> BaCl2

Question 5

What is the reaction of group 2 elements from Mg to Ba when reacted with water?

Answer 5

Mg + 2H2O -> Mg(OH)2 + H2
Ca + 2H2O -> Ca(OH)2 + H2

Question 6

What is the special reaction of magnesium and steam?

Answer 6

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

Question 7

What is the reaction of oxides with dilute acid?

Answer 7

MgO (s) + 2HCl (aq) -> MgCl2 + H2O
CaO (s) + H2SO4 (aq) -> CaSO4 (aq)+ H2O (l)

Question 8

what is the reaction of hydroxides with dilute acid?

Answer 8

2HNO3 (aq) + Mg(OH)2 -> Mg(NO3)2 (aq) + 2H2O
2HCl (aq) + Mg(OH)2 (aq) -> MgCl2 (aq) +2H2O (l)

Question 9

what are the trends in solubility of the hydroxides and sulfates

Answer 9

• Solubility of group 2 hydroxides become MORE soluble down the group.
  if not soluble, hydroxides appear as white precipitates
• Group 2 sulfates become LESS soluble down the group (e.g. MgSO4 (most soluble) and BaSO4 (least) as barium sulfate is used to test for sulfate ions in a solution

Question 10

what is thermal stability?

Answer 10

how stable a compound is when heated

Question 11

what reasons are there to explain the trends in thermal stability of nitrates and carbonates of elements in group 1 and 2?

Answer 11

A small 2+ ion has a lot of charge packed into a small volume of space. It will have a HIGH CHARGE DENSITY and will have a marked distorting effect on any negative ions which are nearby.

A larger 2+ ion has the SAME charge spread over a larger volume of space. LOWER CHARGE DENSITY, less distortion to nearby negative ions.

Question 12

describe thermal stability of a group 1 and 2 carbonate ion

Answer 12

the positive ion attracts delocalised electrons in the carbonate ion towards itself = polarised.
When heated, it decomposes, releasing CO2 from the metal oxide.
The amount of heat depends on how polarised the ion is…. HIGHLY POLARISED = LESS HEAT

Question 13

how is a characteristic flame colours by Group 1 and 2 compounds formed ?

Answer 13

In a flame test, heat causes the electron to move to a HIGHER ENERGY LEVEL.
- The electron is unstable at the higher energy level so it drops back down.
- As it drops down an energy level, energy is emitted as visible light within the wavelength of observed light.

Question 14

what are the flame colours of group 1 compounds?

Answer 14

• Li = red
  -Na = orange/yellow
• K = lilac
• Rb = red/purple
• Cs = blue/violet

Question 15

what are the flame colours of group 2 compounds?

Answer 15

Be = n/a
Mg = n/a
Ca= brick red
Sr= crimson red
Ba = apple green

Question 16

Name the experimental procedure to show:
1- patterns in thermal decomposition of group 1 and 2 nitrates and carbonates
2- flame colours in compunds of group 1 and 2 elements

Answer 16

METHOD- NICHROME WIRE
- nichrome (or platinum) is an unreactive metal and will not give off any flame colour
1. clean the wire by dipping it in concentrated HCl acid
2. heat in a bunsen flame
3. ensure the sample is grinded and powdered
4. hold the end of the wire and dip wire in the solid and place in the bunsen flame and observe the colour made

Question 17

reasons for the trend in MP and BP for group 7 elements

Answer 17

INCREASES down the group
molecules and their electron clouds become larger, greater no of electrons therefore greater London forces between molecules
As the intermolecular forces of the instantaneous dipole - induced dipole attraction therefore more energy is needed to overcome these forces.

Question 18

describe the physical state and electronegativities of group 7 halogens

Answer 18

Physical state
- F2 = gas
- Cl2= gas
- Br2= liquid
- I2= solid

Electronegativity DECREASES down the group (due to the increase of inner electron shells and increase in distance from the nucleus)

Question 19

what is the trend of reactivity of group 7 halogens

Answer 19

LESS REACTIVE DOWN THE GROUP

• atoms become larger, outer electrons further away from the nucleus
• outer electrons are shielded more from the attraction of the positive nucleus due to MORE inner electrons
• harder to attract electrons to form an ion

Question 20

Describe the trend of reactivity of group 7 elements in terms of redox reactions of Cl2, Br2 and I2

Answer 20

DECREASES DOWN THE GROUP
- Group 7 elements cause the oxidation of other compounds -> a good oxidising agent
- Elements gain electrons LESS readily so their oxidising power DECREASES, therefore a more reactive halogen will displace a less reactive one.

Question 21

understand in terms of changes in oxidation number
i oxidation reactions between group 1 and 2
metals

Answer 21

when halogens react they’re reduced and they oxidise other substances
in an oxidation reaction, they produce halide salts
e.g. Mg (s) + Cl2 (g) -> MgCl2 (s)

 magnesium is oxidised: 0 -> +2
 chlorine is reduced: 0 -> -1

Question 22

ii -the disproportionation reaction of chlorine with water and the use of chlorine in water treatment

Answer 22

Cl2 (g) + H2O (l) -> HCl (aq) + HClO (aq)

oxidation: Cl2 -> 2Cl- + 2e- oxidation state: 0-> +1
reduction: Cl2 + 2e- -> 2Cl- oxidation state: 0->-1

(hypochlorus acid ionises to make chlorate (I) ions aka hypochlorite ions)

Question 23

iii- the disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide to form bleach

Answer 23

2NaOH (aq) + Cl2 (g) -> NaClO (aq) + NaCl (aq) + H2O (l)

oxidation: Cl2 -> 2Cl- + 2e-
(oxidation number: 0 -> 1+)
reduction: Cl2 + 2e- -> 2Cl-
(oxidation number: 0 -> -1)

Question 24

iv- the disproportionation reaction of chlorine with hot alkali

Answer 24

3Cl2 + 6NaOH -> 5NaCl + NaClO2 + 3H2O
0 1-
0 5+
oxidation: Cl2 -> 10e- + 2Cl+5
reduction: Cl2 +2e- -> 2Cl-

Question 25

13. ii- reaction of solid group 1 halides with concentrated sulfuric acid to illustrate the trend in reducing ability of the hydrogen halides (sodium chloride)

Answer 25

SULFURIC ACID AND SODIUM CHLORIDE

NaCl + H2SO4 -> NaHSO4 + HCl

observation: misty fumes
products: HCl

Question 26

13 i concentrated sulfuric acid and sodium bromide (equation, half equations, observations and products)

Answer 26

NaBr + H2SO4 -> NaHSO4 + HBr
Half equations: 2Br- -> Br2 + 2e-
H2SO4 + 2HBr -> 2H2O + SO2 + Br2

OBservations: misty and brown fumes, colourless gas with a choking smell

Products: HBr, bromide and sulfur dioxide

Question 27

13 i concentrated sulfuric acid and sodium iodide (equation, observations and half equations)

Answer 27

NaI + H2SO4 -> HI + NaHSO4

half equations: 2I- -> I2 + 2e-
                            H2SO4 + 6H+ +6e- -> 4H2O + S 6I- + H2SO4 + 6H+ -> 4H2O + S + 3I2

Observations: Misty fumes, purple fumes/ black solid, colourless gas with choking smell and one smelling like rotten eggs, and a yellow solid

Products: Hydrogen iodide, iodine, sulfur dioxide, sulfur, hydrogen sulfide

Question 28

13 ii- describe the precipitation reaction of aqueous solution of Cl- with aqueous silver nitrate solution, followed by aqueous ammonia solution

Answer 28

silver nitrate- white precipitate forms
dilute ammonia- soluble

Question 29

13 ii- precipitation reaction of Br- when reacted with silver nitrate and dilute ammonia

Answer 29

silver nitrate= cream precipitate
dilute ammonia= insoluble

Question 30

13 ii- precipitation reaction of I- IONS WHEN REACTED WITH SILVER NITRATE AND DILUTE AMMONIA

Answer 30

silver nitrate- yellow precipitate
dilute ammonia= insoluble