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Y4 RGS Chemistry > QA (qualitative analysis) - anions + gas test > Flashcards

QA (qualitative analysis) - anions + gas test Flashcards

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1
Q

Anions are usually identified by:
- ______ test reagents and _______ tests
- ____ evolved during heating/reaction with dilute acids

A

Anions are usually identified by:
- Specific test reagents and confirmatory tests
- Gas evolved during heating/reaction with dilute acids

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2
Q

What do you need to write down for identity of gas evolved?

A
  • colour
  • smell
  • test
  • identity
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3
Q

Carbonate ion, (CO3)2- and dilute acids: what do you observe?

A

Add any dilute acid. Pass the gas given off into limewater.
- Effervescence is observed. Colourless, odourless gas evolved forms a white precipitate when bubbled into limewater (aq calcium hydroxide). Gas is CO2.

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4
Q

Carbonate ion, (CO3)2- and aq. BaCl2 + dilute HCl / Ba(NO3)2 + dilute HNO3: what do you observe?

A

White precipitate formed. Precipitate soluble in acid to form a colourless solution.
Effervescence is observed. Colourless, odourless gas evolved forms a white precipitate when bubbled into limewater (aq calcium hydroxide). Gas is CO2.

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5
Q

Carbonate ion, (CO3)2- and aq. AgNO3 + dilute HNO3: what do you observe?

A

White precipitate formed. Precipitate turned pale yellow on standing.
Precipitate dissolves in dilute acid to form a colourless solution.
Effervescence is observed. Colourless, odourless gas evolved forms a white precipitate when bubbled into limewater (aq calcium hydroxide). Gas is CO2.

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6
Q

Carbonate ion, (CO3)-2 and aq Pb(NO3)2 followed by dilute HNO3: what do you observe?

A

White precipitate formed.
Precipitate soluble in acid to form a colourless solution.
Effervescence is observed. Colourless, odourless gas evolved forms a white precipitate when bubbled into limewater (aq calcium hydroxide). Gas is CO2.

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7
Q

Sulfate ion, SO4-2 and aq. BaCl2 + dilute HCL / Ba(NO3)2 + dilute HNO3 / Pb(NO3)2 + dilute HNO3: what do you observe?

A

White precipitate formed. Precipitate is insoluble in acid.

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8
Q

Chlorine ion, Cl- and aq AgNO3 + dilute HNO3 + aq NH3: what do you observe?

A

White ppt formed, ppt insoluble in acid
Ppt soluble in aq NH3 to form a colourless solution

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9
Q

Chlorine ion, Cl- and aq Pb(NO3)2 + dilute HNO3: what do you observe?

A

White ppt formed. Ppt insoluble in acid

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10
Q

Iodine ion, l- and aq AgNO3 + dilute HNO3 + aq NH3: what do you observe?

A

Yellow ppt formed. Ppt is insoluble in acid.
Ppt is insoluble in aq NH3.

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11
Q

Iodine ion, l- and aq Pb(NO3)2 + dilute HNO3: what do you observe?

A

Yellow ppt formed. Ppt insoluble in acid.

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12
Q

Nitrate ion, NO3- and aq NaOH + Devarda’s alloy / zinc / aluminium foil, warmed: what do you observe?

A

On warming, effervescence is observed. Colourless and pungent gas evolved which turns moist red litmus paper blue. Ammonia gas, NH3 (g) is evolved.

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13
Q

What is one purpose of adding acid?

A

Purpose of acids: remove any carbonate impurities that may be present/detect presence of carbonate ion (effervescence, gas evolved is CO2)

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14
Q

Test + results for ammonia gas, NH3?

A

Place a piece of moist red litmus paper at the mouth of the test tube
Colourless and pungent gas evolved which turns moist red litmus paper blue

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15
Q

Test + results for chlorine gas, Cl2?

A

Place a piece of moist blue litmus paper at the mouth of the test tube
Pale greenish-yellow and pungent gas evolved which turns moist blue litmus paper red and then bleached (litmus paper turns white)

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16
Q

Test + results for water vapour, H2O?

A

Place a piece of cobalt (II) chloride paper at the mouth of the test tube
Colourless and odourless gas evolved which turned blue cobalt (II) chloride paper pink.

17
Q

Test + results for sulfur dioxide, SO2?

A

Place a piece of filter paper soaked with acidified potassium manganate (VII) solution at the mouth of the test tube
Colourless and pungent gas evolved which turns purple acidified potassium manganate (VII) colourless -> KMnO4 (aq)

18
Q

Test + results for carbon dioxide, CO2?

A

Bubble the gas through limewater (calcium hydroxide solution)
Colourless and odourless gas evolved which forms a white precipitate when gas is bubbled into limewater (white ppt: calcium carbonate)

19
Q

Test + results for oxygen, O2?

A

Insert a glowing splint into the test tube
Colourless and odourless gas evolved which relights/rekindles the glowing splint

20
Q

Test + results for hydrogen, H2?

A

Place a lighted splint at the mouth of the test tube
Colourless and odourless gas evolved which extinguished the lighted split with a “pop” sound

Y4 RGS Chemistry (5 decks)

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