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Inorganic QA (identify from test results) Flashcards

1
Q

Upon addition of NaOH(aq), no ppt formed. What could it be?

A

K⁺, Na⁺, Ba²⁺
Effervescence observed:
- NH3 upon heating: NH4⁺
- H2: Zn or Al in water

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2
Q

What is the equation for NH4⁺ upon addition of NaOH(aq)?

A

NH4⁺ (aq) + OH⁻ (aq) → NH3 (g)+ H2O (l)

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3
Q

What is the equation of Al in water upon addition of NaOH(aq)?

A

2Al (s) + 2OH⁻ (aq) + 6H2O (l)→ 3H2 (g)+ 2[Al(OH)4]⁻ (aq)

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4
Q

What is the equation of Zn in water upon addition of NaOH(aq)?

A

Zn (s) + 2OH⁻ (aq) + 2H2O (l) → [Zn(OH)₄]²⁻ (aq) + H2 (g)

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5
Q

Upon addition of NaOH(aq), white ppt. formed. What could it be?

A
  • Ppt. soluble in excess NaOH to form colourless solution: Al³⁺, Zn²⁺
  • Ppt. insoluble in excess NaOH: Ca²⁺, Mg²⁺
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6
Q

What is the equation of Al³⁺ upon addition of NaOH(aq)?

A

Al³⁺ (aq) + 3OH⁻ (aq) → Al(OH)₃ (s)
Al(OH)₃ (s) + OH⁻ (aq) → [Al(OH)₄]⁻ (aq)

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7
Q

What is the equation of Zn²⁺ upon addition of NaOH(aq)?

A

Zn²⁺ (aq) + 2OH⁻ (aq) → Zn(OH)₂ (s)
Zn(OH)₂ (s) + 2OH⁻ (aq) → [Zn(OH)₄]²⁻ (aq)

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8
Q

What is the equation of Ca²⁺ upon addition of NaOH(aq)?

A

Ca²⁺ (aq) + 2OH⁻ (aq) → Ca(OH)₂ (s)

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9
Q

What is the equation of Mg²⁺ upon addition of NaOH(aq)?

A

Mg²⁺ (aq) + 2OH⁻ (aq) → Mg(OH)₂ (s)

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10
Q

Upon addition of NaOH(aq), cream ppt. formed. What could it be?

A

Ppt. insoluble in excess NaOH (aq), ppt. turned brown on standing in air: Mn²⁺

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11
Q

What is the equation of Mn²⁺ upon addition of NaOH(aq)?

A

Mn²⁺ (aq) + 2OH⁻ (aq) → Mn(OH)₂ (s)
4Mn(OH)₂ (s) + O₂ (g) +2H2O (l) → 4Mn(OH)₃ (s)
{oxidation}

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12
Q

Upon addition of NaOH(aq), grey-green ppt. formed. What could it be?

A

Ppt. soluble in excess NaOH(aq) to form a dark green solution: Cr³⁺

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13
Q

What is the equation of Cr³⁺ upon addition of NaOH(aq)?

A

Cr³⁺ (aq) + 3OH⁻ (aq) → Cr(OH)₃ (s)
Cr(OH)₃ (s) + 3OH⁻ (aq) → [Cr(OH)₆]³⁻ (aq)

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14
Q

Upon addition of NaOH(aq), green ppt. formed. What could it be?

A

Ppt. insoluble in excess NaOH(aq), ppt. turned brown on standing in air: Fe²⁺

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15
Q

What is the equation of Fe²⁺ upon addition of NaOH(aq)?

A

Fe²⁺ (aq) + 2OH⁻ (aq) → Fe(OH)₂ (s)
4Fe(OH)₂ (s) + O₂ (g) +2H2O (l) → 4Fe(OH)₃ (s)
{oxidation}

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16
Q

Upon addition of NaOH(aq), red-brown ppt. formed. What could it be?

A

Ppt. insoluble in excess: Fe³⁺

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17
Q

What is the equation of Fe³⁺ upon addition of NaOH(aq)?

A

Fe³⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s)

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18
Q

Upon addition of NaOH(aq), pale blue ppt. formed. What could it be?

A

Ppt. insoluble in excess, ppt. turned black upon boiling: Cu²⁺

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19
Q

Upon addition of NH₃(aq), no ppt. formed. What could it be?

A

Ba²⁺, Ca²⁺ , NH4⁺

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20
Q

Upon addition of NH₃(aq), white ppt. formed. What could it be?

A
  • Soluble in excess to give a colourless solution: Zn²⁺
  • Insoluble in excess: Al³⁺, Mg²⁺
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21
Q

What is the equation of Zn²⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)

Zn²⁺ (aq) + 2OH⁻ (aq) → Zn(OH)₂ (s)

Zn(OH)₂ (s) + 4NH₃ (aq) → [Zn(NH₃)₄]²⁺ (aq) + 2OH⁻ (aq)

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22
Q

What is the equation of Al³⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)
Al³⁺ (aq) + 3OH⁻ (aq) → Al(OH)₃ (s)

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23
Q

What is the equation of Mg²⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)
Mg²⁺ (aq) + 2OH⁻ (aq) → Mg(OH)₂ (s)

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24
Q

Upon addition of NH₃(aq), off-white ppt. formed. What could it be?

A

ppt. insoluble in excess NH3(aq), ppt. turned brown on standing in air: Mn²⁺

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25
Q

What is the equation of Mn²⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)

Mn²⁺ (aq) + 2OH⁻ (aq) → Mn(OH)₂ (s)

4Mn(OH)₂ (s) + O₂ (g) +2H2O (l) → 4Mn(OH)₃ (s)
{oxidation}

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26
Q

Upon addition of NH₃(aq), grey-green ppt. formed. What could it be?

A

Ppt. insoluble in excess NH3: Cr³⁺

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27
Q

What is the equation of Cr³⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)
Cr³⁺ (aq) + 3OH⁻ (aq) → Cr(OH)₃ (s)

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28
Q

Upon addition of NH₃(aq), green ppt. formed. What could it be?

A

ppt. insoluble in excess NH3(aq), ppt. turned brown on standing in air: Fe²⁺

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29
Q

What is the equation of Fe²⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)
Fe²⁺ (aq) + 2OH⁻ (aq) → Fe(OH)₂ (s)

4Fe(OH)₂ (s) + O₂ (g) +2H2O (l) → 4Fe(OH)₃ (s)
{oxidation}

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30
Q

Upon addition of NH₃(aq), red-brown ppt. formed. What could it be?

A

ppt. insoluble in excess NH3(aq): Fe³⁺

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31
Q

What is the equation of Fe³⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)

Fe³⁺ (aq) + 3OH⁻ (aq) → Fe(OH)₃ (s)

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32
Q

Upon addition of NH₃(aq), blue ppt. formed. What could it be?

A

ppt. soluble in excess to form a dark blue solution: Cu²⁺

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33
Q

What is the equation of Cu²⁺ upon addition of NH₃(aq)?

A

NH₃(aq) + H2O (l) ⇌ NH4⁺ (aq) + OH⁻ (aq)

Cu²⁺ (aq) + 2OH⁻ (aq) → Cu(OH)₂ (s)

Cu(OH)₂ (s) + 2H2O (l) + 4NH3 (aq) → [Cu(NH3)₄(H2O)₂]²⁺ (aq) + 2OH⁻ (aq)

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34
Q

Why is there no ppt. produced upon adding NH3 in Ca²⁺ solution but white ppt. produced upon adding NaOH?

A

NH₃ is a relatively weak base with lower [OH⁻] compared than NaOH, it does not precipitate hydroxides of relatively high solubility product

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35
Q

Upon addition of Na₂CO₃ (aq), no ppt. formed. What could it be?

A

Upon warming, effervescence observed. Colourless and pungent gas turns moist red litmus paper blue, NH3(g) evolved: NH₄⁺

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36
Q

What is the equation of Cu²⁺ upon addition of NaOH(aq)?

A

Cu²⁺ (aq) + 2OH⁻ (aq) → Cu(OH)₂ (s)
Cu(OH)₂ → CuO (s) + H2O (l){decomposition}

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37
Q

What is the equation of NH₄⁺ upon addition of Na₂CO₃ (aq)?

A

CO₃²⁻ (aq) + H2O (l) ⇌ HCO3⁻ (aq) + OH⁻ (aq)
NH4⁺ (aq) + OH⁻ (aq) → NH3 (g) + H2O (l)

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38
Q

Upon addition of Na₂CO₃ (aq), white ppt. formed. What could it be?

A

Ppt. insoluble in excess: Ba²⁺, Ca²⁺, Mg²⁺, Zn²⁺
Effervescence observed, white ppt. formed with a colourless, odourless gas that gave white ppt. with limewater, CO2 evolved: Al³⁺

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39
Q

What is the equation of Al³⁺ upon addition of Na₂CO₃ (aq)?

A

Hydrolysis occurs due to high charge density:
[Al(H₂O)₆]³⁺ (aq) ⇌ [Al(H₂O)₅OH]²⁺ (aq) + H⁺ (aq)

CO₃²⁻ (aq) + 2H⁺ (aq) → CO₂ (g) + H₂O (l)

Removal of H⁺ shifts the position of equilibrium of hydrolysis to the right
2[Al(H₂O)₆]³⁺ (aq) + 2CO₃²⁻ (aq) → 2[Al(H₂O)₃(OH)₃] (s) + 3CO₂ (g) + 3H₂O (l)

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40
Q

Upon addition of Na₂CO₃ (aq), off-white ppt. formed. What could it be?

A

Ppt. turned brown on heating: Mn²⁺

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41
Q

What is the equation of Mn²⁺ upon addition of Na₂CO₃ (aq)?

A

Mn²⁺ (aq) + CO₃²⁻ (aq) → MnCO₃ (s)
2MnCO₃ (s) + O₂ (g) → 2MnO₂ (s) + 2CO₂ (g)
{oxidation}

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42
Q

What is the equation of Ba²⁺ upon addition of Na₂CO₃ (aq)?

A

Ba²⁺ (aq) + CO₃²⁻ (aq) → BaCO₃ (s)

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43
Q

What is the equation of Ca²⁺ upon addition of Na₂CO₃ (aq)?

A

Ca²⁺ (aq) + CO₃²⁻ (aq) → CaCO₃ (s)

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44
Q

What is the equation of Mg²⁺ upon addition of Na₂CO₃ (aq)?

A

Mg²⁺ (aq) + CO₃²⁻ (aq) → MgCO₃ (s)

45
Q

What is the equation of Zn²⁺ upon addition of Na₂CO₃ (aq)?

A

Zn²⁺ (aq) + CO₃²⁻ (aq) → ZnCO₃ (s)

46
Q

Upon addition of Na₂CO₃ (aq), grey-green ppt. formed. What could it be?

A

Colourless and odourless gas gave white ppt. with limewater, CO2 (g) evolved: Cr³⁺

47
Q

What is the equation of Cr³⁺ upon addition of Na₂CO₃ (aq)?

A

Hydrolysis occurs due to high charge density:
[Cr(H₂O)₆]³⁺ (aq) ⇌ [Cr(H₂O)₅OH]²⁺ (aq) + H⁺ (aq)

CO₃²⁻ (aq) + 2H⁺ (aq) → CO₂ (g) + H₂O (l)

Removal of H⁺ shifts the position of equilibrium of hydrolysis to the right
2[Cr(H₂O)₆]³⁺ (aq) + 2CO₃²⁻ (aq) → 2[Cr(H₂O)₃(OH)₃] (s) + 3CO₂ (g) + 3H₂O (l)

48
Q

Upon addition of Na₂CO₃ (aq), green ppt. formed. What could it be?

A

Ppt. insoluble in excess: Fe²⁺

49
Q

What is the equation of Fe²⁺ upon addition of Na₂CO₃ (aq)?

A

Fe²⁺ (aq) + CO₃²⁻ (aq) → FeCO₃ (s)

50
Q

Upon addition of Na₂CO₃ (aq), blue ppt. formed. What could it be?

A

Ppt. turned black on boiling: Cu²⁺

51
Q

What is the equation of Cu²⁺ upon addition of Na₂CO₃ (aq)?

A

Cu²⁺ (aq) + CO₃²⁻ (aq) → CuCO₃ (s)
Upon heating:
CuCO₃ (s) → CuO (s) + CO₂ (g)

52
Q

Upon addition of Na₂CO₃ (aq), red-brown ppt. formed. What could it be?

A

Effervescence observed, colourless and odourless gas evolved gave white ppt. in limewater, CO₂ (g) evolved: Fe³⁺

53
Q

What is the equation of Fe³⁺ upon addition of Na₂CO₃ (aq)?

A

Hydrolysis occurs due to high charge density:
[Fe(H₂O)₆]³⁺ (aq) ⇌ [Fe(H₂O)₅OH]²⁺ (aq) + H⁺ (aq)

CO₃²⁻ (aq) + 2H⁺ (aq) → CO₂ (g) + H₂O (l)

Removal of H⁺ shifts the position of equilibrium of hydrolysis to the right
2[Fe(H₂O)₆]³⁺ (aq) + 2CO₃²⁻ (aq) → 2[Fe(H₂O)₃(OH)₃] (s) + 3CO₂ (g) + 3H₂O (l)

54
Q

Why upon addition of Na₂CO₃ (aq), some metal cations form insoluble hydroxides instead of carbonates?

A

Metal cations with high charge density (Fe³⁺, Cr³⁺, Al³⁺) have highly polarising cations that distort the electron clouds of the water molecules in the hexaaqua metal complex, thus weakening their O-H bonds, thus these cations hydrolyses in water to produce H₃O⁺

55
Q

Upon addition of AgNO₃ (aq), white ppt. formed. What could it be?

A
  • Ppt. turned yellow-brown on standing, ppt. soluble in dilute HNO₃ (aq), CO₂ (g) evolved: CO₃²⁻
  • ppt. soluble in HNO₃, SO₂ (g) evolved: SO₃²⁻
  • ppt. insoluble in HNO₃: SO₄²⁻ or Cl⁻
    * Add excess NH₃(aq): ppt. soluble in excess NH₃ (aq) to give a colourless solution [Ag(NH₃)₂]⁺: Cl⁻
56
Q

What is the equation when you add excess NH3(aq) into AgX (aq)?

A
  • AgX (s) ⇌ Ag⁺ (aq) + X⁻ (aq)
  • Ag⁺ (aq) + 2NH₃ (aq) ⇌ [Ag(NH₃)₂]⁺ (aq)
57
Q

Upon addition of AgNO₃ (aq), cream ppt. formed. What could it be?

A
  • Ppt. insoluble in dilute HNO₃
  • Ppt. partially soluble in excess NH₃ (aq) to give a colourless solution of [Ag(NH₃)₂]⁺: Br⁻
58
Q

Upon addition of AgNO₃ (aq), yellow ppt. formed. What could it be?

A
  • ppt. insoluble in dilute HNO₃
  • ppt. insoluble in NH₃ (aq): I⁻
59
Q

Upon addition of AgNO₃ (aq), red-brown ppt. formed. What could it be?

A

CrO₄²⁻

60
Q

What happens when Ag₂SO₃ is warmed?

A

Observation: SO2 evolved
Equation: 2Ag₂SO₃ (s) → 2Ag(s) + Ag₂SO₄ (s) + SO₂ (g)

61
Q

What happens when you expose white ppt. of AgCl (s) to light or left to stand?

A

Observation: Cl2 evolved
Equation: 2AgCl (s) → 2Ag(s) + Cl₂ (g)

62
Q

Upon addition of KMnO₄ (aq), solution remains purple. What could it be?

A

Observation: effervescence observed, white ppt. formed with limewater, CO₂ evolved: CO₃²⁻

63
Q

Upon addition of KMnO₄ (aq), purple KMnO₄ decolourises. What could it be?

A
  • Cl₂ evolved; greenish-yellow pungent gas evolved turned moist blue litmus red then bleached it: Cl⁻
  • Br₂ evolved; reddish-brown pungent gas evolved fromed an orange solution when passed into water, orange solution turned colourless on addition of NaOH (aq): Br⁻
  • Black deposits in brown solution formed: I⁻
  • Add K₂Cr₂O₇ (aq): orange Cr₂O₇²⁻ turned green Cr³⁺: NO₂⁻ or SO₃²⁻
64
Q

Upon addition of Pb(NO₃)₂ (aq), white ppt. formed. What could it be?

A
  • soluble in dilute acid and CO₂ evolved: CO₃²⁻
  • ppt. soluble in hot water to give a colourless solution, ppt. reappeared upon cooling: Cl⁻ or Br⁻
    * ppt. soluble in conc. HCl to give a colourless solution of [PbCl₄]²⁻: Cl⁻
  • ppt. insoluble in hot water ppt. soluble in dilute acids to give SO₃: SO₃²⁻
  • ppt. insoluble in hot water ppt. insoluble in strong dilute acids: SO₄²⁻
65
Q

Upon addition of Pb(NO₃)₂ (aq), yellow ppt. formed. What could it be?

A
  • ppt. soluble in dilute acids to give an orange solution: CrO₄²⁻
  • ppt. soluble in hot water to give a colourless solution, ppt. reappeared as golden crystals upon cooling: I⁻
66
Q

What can KI (aq) be used for?

A
  • as a reducing agent (to test for oxidising agent)
  • as a precipitant
67
Q

How to prepare KI to test for precipitant?

A

To about 1-2cm³ of aqueous test sample, add a few drops of KI (aq)

68
Q

How to prepare KI to test as a reducing agent (test for oxidising agent)?

A
  • Add approximately equal volume of dilute H₂SO₄ to 1-2cm³ of the test sample (if acidic condition is required)
  • Add KI (aq) dropwise until no more change is observed

(basically acidified KI)

69
Q

Upon addition of acidified KI (aq), cream ppt. formed in brown solution. What could it be?

Additional tests, equation

A
  • 2Cu²⁺ (aq) + 4I⁻ (aq) → 2CuI (s) + I₂ (aq)
  • On addition, of NaS₂O₃ (aq), brown solution turned colourless: Cu²⁺
  • 2S₂O₃²⁻ + I₂ (aq) → S₄O₆²⁻ (aq) + 2I⁻ (aq)
70
Q

What can K₂Cr₂O₇ (aq) be used to test for?

A
  • precipitate insoluble chromate(VI)
  • test for acidic solutions
71
Q

Upon addition of acidified K₂Cr₂O₇ (aq), yellow ppt. formed. What could it be?

Additional test

A

ppt. insoluble in NaOH (aq): Ba²⁺

72
Q

Upon addition of acidified K₂Cr₂O₇ (aq), brown ppt. formed. What could it be?

73
Q

Upon addition of acidified K₂Cr₂O₇ (aq), orange-brown ppt. formed. What could it be?

74
Q

Upon addition of acidified K₂Cr₂O₇ (aq), solution turns from orange to yellow. What does this mean?

A

Solution is alkali
Cr₂O₇²⁻ (aq) + 2OH⁻ (aq) → 2CrO₄²⁻ (aq) + H₂O (l)

(Reverse can also work if solution is acidic)

75
Q

Upon addition of BaCl₂ (aq) or Ba(NO₃)₂ (aq), followed by dilute acids, white ppt. formed. What could it be?

A
  • ppt. soluble in dilute acids
    * CO₂ (g) evolved: CO₃²⁻
    * SO₂ (g) evolved: SO₃²⁻
  • ppt. insoluble in dilute acids: SO₄²⁻
76
Q

Upon addition of BaCl₂ (aq) or Ba(NO₃)₂ (aq), followed by dilute acids, yellow ppt. formed. What could it be?

A

-ppt. soluble in dilute acids to give orange solution: CrO₄²⁻

77
Q

What can HCl (aq) or H₂SO₄ (aq) be used for?

A
  1. Cation test
  2. Anion test
  3. Redox reagent
  4. HCl test for strong oxidising agent
  5. H₂SO₄ (aq) provide acidic medium for redox reaction
78
Q

Upon addition of HCl (aq) or H₂SO₄ (aq), white ppt. formed. What could it be?

A

Ag⁺, Pb²⁺, Ba²⁺

79
Q

What are the possible observations when HCl (aq) or H₂SO₄ (aq) is used to test for anions?

A
  • CO₂ (g) evolved: CO₃²⁻
  • SO₂ (g) evolved: SO₃²⁻
  • NO₂ (g) evolved: NO₂⁻
  • orange solution turned yellow: CrO₄²⁻
80
Q

How can HCl (aq) be used to test for strong oxidising agents?

A

HCl can be an oxidising or reducing agent, with a strong oxidising agent, it will be oxidised

81
Q

Why is H₂SO₄ (aq) used to provide acidic medium instead of HNO₃ or HCl?

A
  • HNO₃ is oxidising agent
  • HCl can be oxidised by strong oxidising agents, HCl itself also can be oxidising agent
82
Q

How to test for water vapour?

A

Colourless, odourless gas that turned blue cobalt(II) chloride paper pink

83
Q

How to test for NO2 (g)?

A
  • Brown, pungent gas turned moist blue litmus paper red
  • turn FeSO₄ from pale green to brown
84
Q

How to test for HCl (g)?

A

Colourless, pungent gas that turns moist blue litmus paper red and forms dense white fumes with NH₃ gas

85
Q

How to test for Br₂ (g)?

A
  • Reddish-brown, pungent gas that forms an orange solution when passed into water
  • The orange solution turned colourless on addition of NaOH (aq)
86
Q

In general, what are the possible deductions and observations upon adding NaOH (aq)?

A
  • identify cations from colour of ppt. and solubility in excess
  • confirm presence of NH₄⁺
87
Q

In general, what are the possible deductions and observations upon adding NH₃ (aq)?

A

identify cations from colour of ppt. and solubility in excess

88
Q

In general, what are the possible deductions and observations upon adding NH₃ (aq)?

A
  • ppt. formed (colour)
  • gas evolved: NH₃, CO₂
89
Q

In general, what are the possible deductions and observations upon adding dilute HCl or dilute H₂SO₄?

A
  • ppt. formed (colour)
  • gas evolved: CO₂, SO₂, NO₂ (or H₂ if metal is present)
90
Q

In general, what are the possible deductions and observations upon adding KI (aq)?

A
  • ppt. formed (colour)
  • yellow or black deposits in brown solution due to liberation of I₂ in presence of oxidising agent
91
Q

In general, what are the possible deductions and observations upon adding K₂Cr₂O₇ (aq)?

A
  • ppt. formed (colour)
  • colour change of the solution
92
Q

In general, what are the possible deductions and observations upon adding AgNO₃ (aq)?

A
  • ppt. formed (colour)
  • solubility of ppt. in NH₃ (aq) and/or dilute acid and gas evolved
93
Q

In general, what are the possible deductions and observations upon adding BaCl₂ or Ba(NO₃)₂ (aq)?

A
  • ppt. formed
  • solubility of ppt. formed in HCl (aq) and gas evolved
94
Q

In general, what are the possible deductions and observations upon adding Pb(NO₃)₂ (aq)?

A
  • ppt. formed
  • solubility of ppt. in hot water and/or acids
95
Q

In general, what are the possible deductions and observations upon adding KMnO₄ (aq)?

A

Colour change of solution

96
Q

What happens when you add conc. HCl dropwise to Cu²⁺ (aq)?

Observation and Equation

A
  • Blue solution turned green then yellow (or yellow-green solution obtained)
  • [Cu(H₂O)₆]²⁺ (aq) + 4Cl⁻ (aq) ⇌ [CuCl₄]²⁻ (aq) + 6H₂O (l)
  • green is due to mixture of [Cu(H₂O)₆]²⁺ and [CuCl₄]²⁻
97
Q

What happens when you add NaOH (aq) until ppt. dissolves followed by heating with H₂O₂(aq) to Cr³⁺ (aq)?

A
  • grey-green ppt. formed, ppt. soluble in excess NaOH(aq) to give a dark green solution [Cr(OH)₆]³⁻ (aq)
    * Cr³⁺ (aq) + 3OH⁻ (aq) → Cr(OH)₃ (s)
    * Cr³⁺ (aq) + 6OH⁻ (aq) → [Cr(H₂O)₆]³⁻ (aq)
  • Upon heating with H₂O₂(aq), a yellow solution formed
    * 2[Cr(H₂O)₆]³⁻ (aq) + 3H₂O₂(aq) → 2CrO₄²⁻ (aq) + 8H₂O(l) + 2OH⁻ (aq)
98
Q

What happens when you add KSCN(aq) dropwise to Fe³⁺ (aq)?

A
  • Blood-red colouration observed
  • [Fe(H₂O)₆]³⁺ (aq) + SCN⁻ (aq) → [Fe(SCN)(H₂O)₅]²⁺ (aq) + H₂O (l)
99
Q

What happens when you add NH₃(aq) followed by adding NH₄Cl(aq) dropwise till excess to Mg²⁺ (aq)?

A
  • white ppt. of Mg(OH)₂ formed
  • ppt. insoluble in NH₃(aq)
  • ppt. soluble in NH₄⁺ (aq)
100
Q

What happens when you add NH₃(aq) followed by adding NH₄Cl(aq) dropwise till excess to Mn²⁺ (aq)?

A
  • cream ppt. of Mn(OH)₂ formed
  • ppt. insoluble in NH₃(aq)
  • ppt. soluble in NH₄⁺ (aq)
101
Q

What happens when you heat NO₃⁻ or NO₂⁻?

A

Brown pungent gas evolved turned moist blue litmus red, NO₂ (g) evolved

102
Q

What happens when you add NaOH(aq) and Al or Zn powder or Devarda’s alloy to NO₃⁻ and warm mixture gently?

A

Colourless, pungent gas evolved turned moist red litmus paper blue, NH₃ (g) evolved

(H₂ is always evolved when NaOH is added to Al or Zn or Devarda’s alloy)

102
Q

What happens when you heat CO₃²⁻?

A

Colourless, odourless gas evolved formed white ppt. with limewater, CO₂ (g) evolved

103
Q

What happens when you add NaOH(aq) and Al or Zn powder or Devarda’s alloy to NO₂⁻ and warm mixture gently?

A

Colourless, pungent gas evolved turned moist red litmus paper blue, NH₃ (g) evolved

(H₂ is always evolved when NaOH is added to Al or Zn or Devarda’s alloy)

104
Q

What happens when you add NaOCl(aq), followed by ethanoic acid CH₃COOH to Br⁻ and add a few drops of organic solvent to the mixture and shake?

A
  • Orange solution Br₂ (aq) formed
  • Organic solvent layer turned orange-red
105
Q

What happens when you add solid MnO₂ and conc. H₂SO₄ to solid sample containing Cl⁻?

A

greenish-yellow pungent gas evolved turned moist blue litmus red then bleached it, Cl₂ (g) evolved

105
Q

What happens when NaOCl(aq), followed by CH₃COOH is added to I⁻, then a few drops of organic solvent is added to mixture and shake?

A
  • Brown solution I₂ (aq) formed
  • Organic solvent layer turned violet
106
Q

What happens when CuSO₄ (aq) is added to I⁻ and then Na₂S₂O₃ (aq) is added till in excess?

A
  • cream ppt. CuI (s) in brown solution I₂ (aq) formed
  • On adding N₂S₂O₃ (aq), brown solution decolourised (I⁻)
107
Q

What happens when dilute HCl is added to I⁻ followed by H₂O₂(aq)?

A

Black deposits in brown solution formed (I₂ liberated)

Chemistry Practical (4 decks)

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