tests

Question 1

test for bromine water

Answer 1

alkenes will decolourise bromine water due to the electrophilic addition of Br2 to alkene

Question 2

test for aldehydes and 1,2 alcohols

Answer 2

acidified potassium dichromate
orange to green
the Cr2O7^2- (orange) is reduced to Cr3+ (green) when an alchol/aldehyde is oxidised

Question 3

test for aldehyde (tollens reagent)

Answer 3

silver mirror forms as the Ag+ is reduced to Ag(s) when the aldehyde is oxidised

Question 4

test for aldehydes (fehlings)

Answer 4

aldehydes turns from blue solution to red brick precipitate
and fehlings solution is reduced when the aldehyde is oxidised

Question 5

test for carboxylic acid

Answer 5

sodium carbonate
effervescence
formation of CO2

Question 6

test for Ba2+

Answer 6

H2SO4
white ppt
formation of BaSO4
Ba2+ (aq) + SO4^2- (aq) -> BaSO4 (s)

Question 7

SO4^2- test

Answer 7

BaCl2
white ppt
formation of BaSO4
Ba2+ (aq) + SO4^2- (aq) -> BaSO4 (s)

Question 8

test for Mg2+

Answer 8

NaOH
white ppt
formation of Mg(OH)2
Mg2+ (aq) + 2OH- (aq) -> Mg(OH)2

Question 9

test for OH-

Answer 9

MgCl2
white ppt
formation of Mg(OH)2
Mg2+ (aq) + 2OH- (aq) -> Mg(OH)2

Question 10

test for Cl-

Answer 10

AgNO3
white ppt
formation of AgCl
Ag+ (aq) +Cl- (aq) -> AgCl (s)

Question 11

test for Br-

Answer 11

AgNO3
cream ppt
formation of AgBr
Ag+ (aq) +Br- (aq) -> AgBr (s)

Question 12

test for I-

Answer 12

AgNO3
yellow ppt
formation of Agl
Ag+ (aq) +l- (aq) -> Agl (s)

Question 13

test for AgCl

Answer 13

dilute NH3
AgCl ppt dissolves
AgCl(s) +2NH3 (aq) -> [Ag(NH3)2]+ (aq) +Cl- (aq)

Question 14

test for AgBr

Answer 14

conc NH3
AgBr ppt dissolves
AgBr(s) +2NH3 (aq) -> [Ag(NH3)2]+ (aq) +Br- (aq)

Question 15

test for NH4+

Answer 15

NaOH and heat
gas released turns red litmus paper blue
formation of NH3
NH4+ (aq) + OH- (aq) -> NH3(g) + H2O (l)

Question 16

test for CO3^2-

Answer 16

any acid (HNO3 is best)
effervescence
formation of CO2
acid + carbonate base -> salt + water + CO2