Chemical Tests Flashcards

1
Q

How do you test for halides in a solution

A

Add silver nitrate + nitric acid

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2
Q

Why add nitric acid when testing for halides within a solution

A

Remove any carbonates which could react with the halide solutions

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3
Q

Sodium nitrate + nitric acid -> halide precipitates

A

Cl- -> white
Br- -> cream
I- -> yellow

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4
Q

Halide in solution precipitates + dilute NH3

A

AgCl —> soluble (dissolves)
AgBr + AgI —> insoluble

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5
Q

Halide in solution precipitates + conc NH3

A

AgBr —> soluble (dissolves)
AgI —> insoluble

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6
Q

How to test for sulphates

A

Aqueous barium chloride + dilute HCl

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7
Q

Why add dilute HCl in test for sulfates

A

So only the sulfate anion will form as the precipitate

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8
Q

Test for sulphates precipitates

A

SO4^2- —> white
SO3^2- —> white
CO3^2- —> White

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9
Q

Test for sulfates precipitates + HCl

A

BaSO4 —> insoluble
BaSO3 —> dissolves
BaCO3 —> dissolves

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10
Q

How to test for solid halide

A

Add a few drops of conc HCl to the halide

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11
Q

Test for solid halide: chloride (observation + inference)

A
  • steamy fumes
  • HCl (g)
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12
Q

Test for solid halide: Bromide (observation + inference)

A
  • Steamy fumes - HBr
  • brown vapour - Br2
  • SO2 (colourless)
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13
Q

Test for solid halide: iodide (observation + inference)

A
  • steamy fumes - HI
  • purple vapour - I2
  • black solid - S
  • yellow solid
  • H2S (colourless)
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14
Q

Halide displacement observations - Cl- (+)

A

Cl2 - no reaction, pale green solution
Br2- no reaction, pale red-brown solution
I2 - no reaction, brown solution

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15
Q

Halide displacement observations - Br- (+)

A

Cl2- red-brown solution, yellow-orange organic layer
Br2- no reaction, pale red-brown solution
I2- no reaction, brown solution

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16
Q

Halide displacement observations - I- (+)

A

Cl2- brown solution, black solid, purple organic layer
Br2- brown solution, black solid, purple organic layer
I2- no reaction, brown solution

17
Q

Difference between I2, Br2 + Cl2 (halide displacement)

A

Br2 + I2 - add organic solvent such as Hexane, will dissolve in the organic layer

18
Q

If CO2 gas given off when heated what could this be

A

Group 2 carbonate, lithium carbonate

19
Q

If O2 gas given off when heated what could this be

A

Group 1 nitrates (except lithium nitrate)

20
Q

If O2 + NO2 gas given off when heated what could this be

A

Group 2 nitrates or lithium nitrate

21
Q

Chemical tests: shake with bromine water

A
  • yellow solution decolorised- alkene
  • yellow solution decolorised + white precipitate form- phenol
22
Q

Chemical tests: warm with aqueous, acidified potassium dichromate (VI)

A

Colour change orange-green —> primary or secondary alcohol, aldehyde

23
Q

Chemical tests: warm with ethanol + aqueous silver nitrate

A
  • white precipitate- choloralkane
  • cream precipitate- bromoalkane
  • yellow precipitate- iodoalkane
24
Q

Chemical tests: warm with ethanol + add a few drops of conc H2SO4. Pour into an aqueous solution of sodium carbonate

A
  • ester smell (e.g. glue smell) - carboxylic acid
25
Q

Chemical tests: phosphorus (V) chloride

A
  • produce steamy fumes that turn damp blue litmus paper blue —> OH group In alcohols, carboxylic acids
26
Q

Chemical tests: warm with Tollens reagent

A

Silver mirror —> aldehyde

27
Q

Chemical tests: heat with Fehlings/Benedict’s reagent

A

Red precipitate —> aldehyde

28
Q

Chemical tests: 2,4-DNPH

A

Orange precipitate —> C=O group in aldehydes, ketones

29
Q

Chemical tests: iodine in alkaline solution

A

Pale yellow precipitate —> methyl ketone or ethanal, methyl secondary alcohol or ethanol