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Chemistry - Things to learn by heart > Chemical tests > Flashcards

Chemical tests Flashcards

Learn all of the chemical tests for ions and functional groups.

1
Q

What is tollens reagent use to test for

A

aldehydes

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2
Q

What is bromine water used to test for

A

alkenes ( Electrophilic addition occurs)

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3
Q

how do you carry out a flame test

A

dip a nicrome wire in hydrochloric acid then dip it in the unknown compound and hold it over a bunson burner

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4
Q

which silver halides dissolve in concentrated ammonia

A

silver chloride and silver iodide

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5
Q

write an equation for the white precipitate formed when using barium ions to test for sulfide ions

A

Ba^2+(aq) + SO4^2+(aq) =) BaSO4(s)

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6
Q

what colour change will indicate a positive result when using bromine water to test for alkenes

A

the solution should go from orange to colourless

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7
Q

What conditions are needed when using fehilings solution to test for aldehydes

A

you need to heat the solution

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8
Q

what can be used to test for carboxylic acids

A

Solid sodium carbonate

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9
Q

How do you test for carbonate ions

A

you add dilute hydrochloric acid ( or any acid)

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10
Q

what factor of hydroxide ions is their chemical test bassed on

A

the fact that they make solutions alkaline

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11
Q

if ammonia is present what colourchange wil be observed on the damp red litmous paper

A

the paper will turn from red to blue

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12
Q

which silver hialides dissolve in dilute ammonia

A

silver chloride

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13
Q

what colour precipitate does bromide give when testing for halide ions

A

A cream precipitate ( of silver bromide)

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14
Q

what is solid sodium carbonate used to test for

A

carboxylic acids

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15
Q

write an equation for how the silver mirror is formed when tollens reagent is mixed with an aldehyde to form a silver mirror

A

Ag+(aq) + e- =) Ag(s)

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16
Q

What does a solution turning from orange to green in acidified potassium dichromate indicate

A

a primary and/or secondary alcohol is present

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17
Q

what is it important to do when using bromine water to test for alkenes

A

shake the test tube

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18
Q

what colour change will indicate a positive resut for fehlings solution

A

a blue solution to a brick red precipitate

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19
Q

when tollings solution is mixed with an aldehyde what colour change is observed

A

the solution will go from colourless to form a silver mirror

20
Q

write an equation to show how potassium dichromate is oxidised when mixed with a primary or secondary alcohol

A

Cr2O7 + 6e- =) 2Cr^3+ + 7H2O

21
Q

in a flame test what colour does barium (Ba^2+) burn

A

pale green

22
Q

What reagent is used to test for primary and secondary alcohols. (HINT: it acts as a reducing agent)

A

Potassium dichromate (VI)

23
Q

in a flame test what colour does calcium (Cu^2+) burn

A

brick red

24
Q

how can you test for ammonium ions

A

using damp red litmous paper

25
Q

how do you test for sulfide ions

A

you add dilute hydrochloric acid followed by barium chloride solution

26
Q

how do you test for hydroxide ions

A

using a PH indicatior for example using red litmous paper if the ions are present the paper will go from red to blue

27
Q

What colour precipitate des iodide give when testing for halide ions

A

a yellow precipitate (of silver iodide)

28
Q

what do you need to do when using red litmious paper to test for ammonium ions

A

you need to add sodium hydroxide to produce ammonia:

NH4+ + OH- =) NH3 + H2O

29
Q

what indicates a positive result when adding hydrochloric acid to a solution to test for carbonate ions

A

the carbonate ions will fizz because CO2 is being produced. It will also turn lime water cloudy

30
Q

What can be used to test for alkenes

A

bromine water

31
Q

What can be used to test for aldehydes

A

Fehlings or benidicts solution (they oxidise aldehydes but not ketones) or tollings reagent

32
Q

what indicates a positive result when solid sodium carbonate is mixed with a carboxylic acid

A

The solution will fizz

if bubbled through limewater in a second test tube it will turn it cloudy (CO2 is produced)

33
Q

How do you test for halide ions (chloride, bromide and iodide)

A

add dilute nitric acid (HNO3)

followed by silver nitrate (AgNO3)

34
Q

how do you prepare tollings reagent

A

you mix silver nitrate and dilute sodium hydroxide then add drops of ammonia solution

35
Q

write an equation fot the reacton of the carbonate ions with the hydrogen ions when using hydrochloric acid to test for caronate ions

A

CO3^2-(aq) + 2H+ =) CO2(g) + H2O(l)

36
Q

colour precipitate does chroride give when testing for halide ions

A

a white precipitate ( of silver chloride)

37
Q

what will be observed when a positive result comes from a test with potassium dichromate to test from primary and secondary alcohols

A

it turns from an orange solution to a green solution

38
Q

what are flame tests used to identify

A

group 2 metals

39
Q

in benedicts solution what are the copper ions dissolved in

A

sodium carbonate

40
Q

in feilings solution what are the copper ions desolved in

A

sodium hydroxide

41
Q

What other conditions are needed when using potassium dichromate to test for primary and secondary alcohols

A

Acidified and heat

42
Q

what does a solution turning brick red (from blue) in fehlings or benidicts indicate ?

A

an aldehyde is present

43
Q

in a flame test what colour does strontium (Sr^2+) burn

A

red

44
Q

when using dilute hydrochloric acid and barium chloride solution to test for sulfide ions what indicates a positive result

A

a white precipitate will form

45
Q

write an equation to show how the copper ions in fehlings solution are oxidised when mixed with an aldehydes

A

Cu^2+ +2OH- + 2e- =) Cu2O + H2O

46
Q

How do you distinguish between primary and secondary alcohols

A
  • oxidise an alcohol under reflux then test for carboxylic acids
  • oxidse an alcohol under distillation then test for an aldehyde
  • oxidise an alcohol under reflux then test for a keytone

Chemistry - Things to learn by heart (3 decks)

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