Test Tube Reactions

Question 1

Describe the test for alkenes

Answer 1

Test: shake with bromine water
Result: colour change from orange to clear

Question 2

describe the test for halo alkanes

Answer 2

test:

• add NaOH(aq) and heat - to substitute the halide ion
• acidify with nitric acid
• add sliver nitrate and precipitates should form
• add dilute ammonia
• then add concentrated ammonia

results:

• AgCl forms white ppt
• AgBr forms cream ppt
• AgI forms yellow ppt
• AgCl white ppt dissolves in dilute ammonia
• AgBr cream ppt dissolves in concentrated ammonia
• AgI is insoluble in ammonia

Question 3

describe the test for primary and secondary alcohols

Answer 3

test: add acidified potassium dichromate
results: colour change from orange to green

Question 4

describe the test for aldehydes

Answer 4

test : add Fehling’s solution / Tollens reagent
results: Fehling’s- colour change from blue to brick red ppt
Tollens- silver mirror forms

Question 5

describe the test for carboxylic acid

Answer 5

test: add NaCO3.
result: efferverscence

Question 6

describe how you would test for the presence of H2 gas

Answer 6

test: apply a lit splinter
result: squeaky ‘pop’ sound

Question 7

describe how you would test for the presence of CO2 gas

Answer 7

test: bubble through lime water
result: solution should turn cloudy

Question 8

describe how you would test for the presence of O2 gas

Answer 8

test: apply a glowing splinter
result: splinter should relight

Question 9

describe how you would test for the presence of SO4^2- ions

Answer 9

test: add BaCl2
result: white ppt forms

Question 10

describe how you would test for the presence of CO3^2- ions

Answer 10

test: add any acid
result: effervescence