group 2 and group 7

Question 1

Group 2 - alkali earth metals

Answer 1

s block metals
react similarly to group 1 but less reactive

Question 2

properties of group 2 elements

Answer 2

atomic radius increases down the group as there’s more shielding
ionisation energy decreases down the group as there’s more shielding
melting point decreases down group - larger molecule-more shielding, less attraction

Question 3

group 2
reactions with water from bases

Answer 3

reactivity increases down group
mg-not very reactive
ba-most reactive

Mg(s)+2H2O(l)—->Mg(OH)2(aq)+H2(g)
slow reaction slow bubbling

Ca(s)+2H20(l)—->Ca(OH)2(aq) +H2(g)
vigorous reaction

Question 4

group 2
reaction with steam

Answer 4

mg slow with water fast with steam
more vigorous

Question 5

group 2 extractions

Answer 5

mg is used to extract titanium from ore
titanium is converted to titanium(IV) chloride by heating with carbon and chlorine gas
purified through fractional distillation then reduced by mg

Question 6

what is wet scrubbing

Answer 6

solution is sprayed onto gas as it leaves
solution-calcium carbonate and oxide removes sulphur dioxide emissions

Question 7

solubility of hydroxides and sulphates

Answer 7

hydroxides (solubility increases) sulphates (solubility decreases)
mg
mg(oh)2 sparingly soluble
MgSo4 completely dissolves
ca
ca(oh)2 sparingly soluble
CaSO4 fairly soluble
sr
sr(oh)2 more soluble
SrSO4 sparingly soluble
ba
ba(oh)2 completely dissolves
BaSO4 insoluble

Question 8

barium sulphate

Answer 8

good at absorbing x rays
-feed patient barium meal
-fills digestion system and when x ray is taken the x rays are absorbed and organs can be seen
toxic but safe as its insoluble

Question 9

test for sulphate ions

Answer 9

add HCl to remove chlorates
add BaCl2
white precipitate forms
sulphate ions present as barium sulphate has been produced

Question 10

milk of magnesia

Answer 10

insoluble-treats indigestion

Question 11

group 7 properties

Answer 11

fluorine-pale yellow gas
chlorine - green gas
bromine - orange/brown liquid
iodine- black solid - vaporise easily

Question 12

melting point and electronegativity group 7

Answer 12

melting point increases down group
all covalent bonding simple molecular with IDD
more electrons down group so stronger IDD

electronegativity decreases down group atomic radius and shielding increase down group

Question 13

reducing strength of halides

Answer 13

reducing agent - electron donor
reducing strength increases down the group as atomic radius increases so weaker attraction between outer electron + nucleus

Question 14

H2SO4 reactions

Answer 14

H2SO4 + Br-.I- —> SO2 acidic gas
H2SO4 +I- —–>S yellow solid
H2SO4 +I- —–> H2S bad egg smell

Question 15

br - + i- equations

Answer 15

2I- —> I2+2e-
2Br- —–>Br2+2e-
chlorine and fluorine too weak reducing agent so undergo acid base reaction with H2SO4
H+ + F- —->HF
NaF + H2SO4—->HF + NaHSO4

H+ + Cl- —>HCl
NaCl + H2SO4 —->HCl + NahSO4

Question 16

H2SO4 Half equations

Answer 16

2H+ + 2e- +H2SO4 —–>SO2 + 2H2O
6H+ + 6e- + H2SO4 —-> S + 4H2O
8H+ +8e- + H2SO4 —-> H2S + 4H20

Question 17

halide tests

Answer 17

add HNO3 - remove carbonates / impurities that may give false positive
add AgNO3
(F-) no precipitate
(Cl-) white precipitate
(Br-) Cream precipitate
(I-) yellow precipitate
add dilute NH3
(F-) NVC
(Cl-) white precipitate dissolves
(Br-) cream precipitate remains
(I-) yellow precipitate remains
Add concentrated NH3
(F-) NVC
(Cl-) NVC
(Br-) cream precipitate dissolves
(I-) yellow precipitate remains

Question 18

silver equations with halides

Answer 18

Ag+(aq) + F-(aq) —> AgF(s)
Ag+(aq) + Cl-(aq) —->AgCl(s)
Ag+(aq) + Br-(aq) —->AgBr(s)
Ag+(aq) + I-(aq) —> AgI(s)

Question 19

oxidising ability of halogens

Answer 19

oxidising agent - electron acceptor
oxidising ability decreases down group as there is a larger radius so weaker attraction between nucleus and incoming electron
more oxidising - displaces from compound
so the higher one in the group displaces

Question 20

observations of halogen displacements

Answer 20

all have NVC BUT
Br- is displaced by Cl2 = aqueous orange solution
I- is displaced by Br2, Cl2 = black solid

Question 21

chlorine

Answer 21

sterilises water - kills bacteria
toxic - but benefits outweigh the risks and only small amounts remain at the end
chlorine + water is a disproportionation equation - cl2 is both oxidised and reduced
Cl2 + H2O >< HCl +HClO
chlorine + NaOH
Cl2 + 2NaOH —> NaCl + NaClO +H2O