4 - Inorganic Chemistry and the Periodic Table

Question 1

what is the trend in thermal decomposition stability down group 1 and 2?

Answer 1

more thermally stable

Question 2

why do the elements in group 1 and 2 get more thermally stable as they go down?

Answer 2

in thermal decomposition, the anion is polarised towards the metal cation. Elements that are more charge dense have a greater polarising ability.

Question 3

equation for thermal decomposition of group 1 metals

Answer 3

e.g KNO3 –> KNO2 + 1/2 O2

Question 4

equation for thermal decomposition of group 2 metals

Answer 4

e.g Ca(NO3)2 –> CaO + 2NO2 + O2

Question 5

equation for thermal decomposition of Lithium

Answer 5

2LiNO3 –> Li20 + 2NO2 + 1/2 O2

Question 6

trend in reactivity with water down group 2 and why

Answer 6

more reactive, because the metals lose their two outer shell electrons, and as you go down the group there is more electron shielding and therefore weaker attraction

Question 7

reaction of magnesium with water observations and equation

Answer 7

very slow reaction with water, burns with white flame to form white powder with steam
water - Mg + 2H2O –> Mg(OH)2 + H2
steam - Mg + H2O –> MgO + H2

Question 8

reaction of calcium with water observations and equation

Answer 8

fizzes in water and after a while a white solid forms - Ca(OH)2 which is slightly soluble in water
Ca + 2H2O –> Ca(OH)2 + H2

Question 9

reaction of strontium with water observations and equation

Answer 9

fizzes in water and forms a colourless solution

Sr + 2H2O –> Sr(OH)2 + H2

Question 10

reaction of barium with water observations and equation

Answer 10

fizzes in water and forms a colourless solution

Ba + 2H2O –> Ba(OH)2 + H2

Question 11

are the group 2 metal oxides ionic or covalent?

Answer 11

all ionic except for BeO which has covalent character

Question 12

trend in solubility down group 2

Answer 12

more soluble

Question 13

trend in how alkaline they are down group 2

Answer 13

more alkaline as more OH- ions formed due to increasing solubility

Question 14

trend in melting points down group 2

Answer 14

decreases down group 2 as weaker metallic bonding due to larger

Question 15

colour of iodine

Answer 15

grey solid, purple vapour as it sublimes easily, purple in organic solvents

Question 16

why do we add HNO3 before AgNO3?

Answer 16

gets rid of trace ions, otherwise those would react with the silver, making silver sulfate or silver carbonate

Question 17

what happens when you put silver nitrate and the halogen in the sunlight

Answer 17

the compound formed decomposes and silver forms, making it grey

Question 18

equation for chlorine acting as an oxidising agent

Answer 18

Cl2 + 2Fe2+ –> 2Fe3+ + 2Cl-

Question 19

disproportionation of halogens in cold alkali equation

Answer 19

Cl2 + 2NaOH –> NaClO + NaCl + H2O

Question 20

disproportionation of halogens in hot alkali equation

Answer 20

3Cl2 + 6NaOH –> NaClO3 + 5NaCl + 3H2O

Question 21

what happens when cyclohexane is added to iodine

Answer 21

layers form, and the top layer goes purple

Question 22

Trend in reducing ability of the halides

Answer 22

Get more reducing power

Bigger ion has more shielding so easier to lose an electron and be oxidised

Question 23

Reaction of fluoride ions with concentrated sulfuric acid

Answer 23

Will not reduce it! Only produce steamy white fumes in the form of HF

Question 24

Reaction of chloride ions with concentrated sulfuric acid

Answer 24

Will not reduce it! Produces steamy white fumes in the form of HCl

Question 25

Reaction of bromide ions with concentrated sulfuric acid

Answer 25

Reduce H2SO4 to SO2 gas

Observe steamy white fumes (HBr) and brown vapour (Br2)

Question 26

Reaction of iodide ions with concentrated sulfuric acid

Answer 26

Reduce H2SO4 to SO2 to S to H2S
Observe steamy white fumes (HI)
purple vapour (Iodine gas)
Grey solid (iodine solid)
Yellow solid (S)
Eggy smell (H2S)