group 7 and 2

Question 1

halide test

Answer 1

1. dissolve in water
2. add HNO3 acid
3. add acidified AgNO3
4. add dilute NH3
5. add acidified NH3

Question 2

why is HNO3 acid added
and equation

Answer 2

to remove any CO3 2- impurities, cause false positives

2Ag+ + CO3 2- —-> Ag2CO (white ppt)

Question 3

what does NH3 do in halide test

Answer 3

forms complex ion - dissolving ppt

AgCl(s) + 2NH3(ag) —-> [Ag(NH3)2]+ (aq) + Cl- (aq)

Question 4

trend in oxidising ability in halogens going down group

Answer 4

• decreases down group
• atomic radius becomes larger
• less attraction between nucleus and incoming e-

Question 5

trend in reducing ability in halides going down group

Answer 5

• increases down group
• ionic radius increases
• less attraction between nucleus and outer e-

Question 6

what happens with solubility to group 2 hydroxides going down group

Answer 6

solubility increases
Mg(OH)2 least soluble

Question 7

what happens to solubility to group 2 sulphates going down group

Answer 7

solubility decreases
BaSO4 least soluble

Question 8

observations when Mg reacts with steam

Answer 8

• white ppt MgO
• white bright light

Question 9

Mg extraction of Ti
and role of Mg

Answer 9

TiCl4 + 2Mg –> 2MgCl2 + Ti
Mg is a reducing agent (being oxidised)