Principles Related to Practical Chemistry — DPP 2

20 NEET questions from Principles Related to Practical Chemistry, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

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1
Metal (M) shows crimson red colour in flame test and its halide is deliquescent. Metal (M) can be:
  1. A Li
  2. B Mg
  3. C Ca
  4. D Ba
Show answer & explanation

Correct answer: A

Metal (Li) shows crimson red colour in flame test and its halide is deliquescent.
Therefore, option (1) is the correct answer.
2
A white flocculants precipitate of $\mathrm { Mg } ^ { 2 + }$ ion with phosphoric salt is:
  1. A $\mathrm { MgHPO } _ { 4 }$
  2. B $\mathrm { Mg } \left( \mathrm { H } _ { 2 } \mathrm { PO } _ { 4 } \right) _ { 2 }$
  3. C $\mathrm { Mg } _ { 3 } \left( \mathrm { PO } _ { 4 } \right) _ { 2 }$
  4. D None of these
Show answer

Correct answer: A

3
Mg is not precipitated in group V. This is because:
  1. A MgCO$_{3}$ is soluble in water
  2. B K$_{sp}$ of MgCO$_{3}$ is high.
  3. C MgCO$_{3}$ is soluble in NH₄OH.
  4. D None of these
Show answer & explanation

Correct answer: B

$\mathrm{MgCO}_{3} \rightleftharpoons \mathrm{Mg}^{2+}+\mathrm{CO}_{3}^{2-}$
The Concentration of $\mathrm{CO}_{3}{ }^{2-}$ ions is very low which does not prevent the ionic product of $\mathrm{Mg}^{2+}$ and $\mathrm{CO}_{3}{ }^{2-}$ ions to surpass the solubility product in the presence of $\mathrm{NH}_{4} \mathrm{Cl}$
Therefore, option (2) is the correct answer.
4
A salt gives white residue in charcoal cavity test but in cobalt nitrate test it gives pink mass. The salt contains which of the following ion?
  1. A $\mathrm { Al } ^ { 3 + }$
  2. B $\mathrm { Zn } ^ { 2 + }$
  3. C $\mathrm { PO } _ { 4 } ^ { 3 - }$
  4. D $\mathrm { Mg } ^ { 2 + }$
Show answer & explanation

Correct answer: B

Mg$^{2+}$ salt gives white residue in charcoal cavity test but in cobalt nitrate test it gives pink mass. In this test, magnesium oxide produced in the charcoal cavity test reacts with CoO in cobalt nitrate test to produce a pink mass due to the formation of MgO.
Therefore, option (2) is the correct answer.
5
When a metal sulphate is heated in dry test tube, the colour changes from blue to white. Then metal sulphate may be:
  1. A $\mathrm { BaSO } _ { 4 }$ (3) $\mathrm { Na } _ { 2 } \mathrm { SO } _ { 4 }$
  2. B $\mathrm { CuSO } _ { 4 } \cdot 5 \mathrm { H } _ { 2 } \mathrm { O }$ (4) None of these
  3. C $\mathrm { Na } _ { 2 } \mathrm { SO } _ { 4 }$
  4. D None of these
Show answer & explanation

Correct answer: B

The colour of hydrated copper sulphate $\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}$ is blue that turns into white, when heated at high temperature in a test tube, due to the loss of water molecules from copper sulphate.
Therefore, option (2) is the correct answer.
6
Which of the following compound is called dead burnt plaster?
  1. A $\mathrm { CaSO } _ { 4 } \cdot \frac { 1 } { 2 } \mathrm { H } _ { 2 } \mathrm { O }$
  2. B $\mathrm { CaSO } _ { 4 } \cdot 2 \mathrm { H } _ { 2 } \mathrm { O }$
  3. C $\mathrm { CaSO } _ { 4 }$ (anhy.)
  4. D None of these
Show answer

Correct answer: C

7
An aqueous solution of a gas (X) decolourizes an acidified K$_{2}$Cr$_{2}$O$_{7}$ solution. On boiling with H₂O₂, cooling it and then adding an aqueous solution of BaCl2, a white ppt. Insoluble in dilute HCl is obtained. Identify (X).
  1. A CO₂
  2. B NH₃
  3. C SO₂
  4. D Cl₂
Show answer & explanation

Correct answer: C

X-SO₂
Reaction:
(i) K$_{2}$Cr$_{2}$O$_{7}$ + H₂SO₄ + 3SO₂ —→ K₂SO₄ + Cr$_{2}$(SO$_{4}$)$_{3}$ + H₂O
(ii) SO₂ + H₂O₂ —→ H₂SO₄
(iii) $\mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{BaCl}_{2} \longrightarrow \underset{\text { (White ppt) }}{\mathrm{BaSO}_{4} \downarrow+2 \mathrm{HCl}}$
Therefore, option (3) is the correct answer
8
In group II radicals, we can not use $\mathrm { H } _ { 2 } \mathrm { SO } _ { 4 }$ in place of HCl because:
  1. A some cations of higher groups i.e. group V will also precipitate as their sulphates.
  2. B some cations of higher groups i.e. group IV will also precipitate as their sulphates.
  3. C $\mathrm { Mg } ^ { 2 + }$ also precipitate as a sulphate.
  4. D All are correct.
Show answer

Correct answer: D

9
A gas turns lime water milky and acidified $\mathrm { K } _ { 2 } \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 }$ solution green. Then gas is:
  1. A HCl
  2. B $\mathrm { H } _ { 2 } \mathrm {S}$
  3. C $\mathrm { SO } _ { 2 }$
  4. D $\mathrm { CO } _ { 2 }$
Show answer & explanation

Correct answer: C

Ca(OH)$_{2}$ + SO₂ $\rightarrow$ CaSO$_{3}$(milky) + H₂O
$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+\mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{SO}_{2} \longrightarrow \underset{\text { (Green) }}{\mathrm{K}_{2} \mathrm{SO}_{4}}+\underset{2}{\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}}+\mathrm{H}_{2} \mathrm{O}$
Therefore, option (3) is the correct answer
10
Which one of the following ions does not give borax bead test?
  1. A Zn$^{2+}$
  2. B Cu$^{2+ }$
  3. C Mn$^{2+}$
  4. D Fe$^{3+}$
Show answer & explanation

Correct answer: A

$\mathrm{Zn}^{2+}$ ions does not give borax bead test, because $\mathrm{Zn}^{2+}$ ion is colourless.
Therefore, option (1) is the correct answer.
11
What happens when solution of $\mathrm { KCl } , \mathrm { KF }$ and KBr are treated with $\mathrm { I } _ { 2 }$ ?
  1. A $\mathrm { Cl } _ { 2 }$ and $\mathrm { Br } _ { 2 }$ are evolved.
  2. B $\mathrm { Cl } _ { 2 }$ is evolved.
  3. C $\mathrm { Cl } _ { 2 } , \mathrm {~F} _ { 2 }$ and $\mathrm { Br } _ { 2 }$ are evolved.
  4. D None of these.
Show answer & explanation

Correct answer: D

$\mathrm{I}_{2}$ is weak oxidising agent. It does not oxidise the $\mathrm{F}^{-}, \mathrm{Cl}^{-}$, $\mathrm{Br}^{-}$ion.
Therefore, option (4) is the correct answer.
12
When H$_{2}$S gas is passed through an ammonical salt solution X, a slightly white precipitate is formed. X can be:
  1. A a cobalt salt
  2. B a lead salt
  3. C a zinc salt
  4. D a silver salt
Show answer & explanation

Correct answer: C

$\mathrm{Zn}^{2+}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{ZnS} \downarrow \text { (white) }+2 \mathrm{H}^{+}$
Therefore, option (3) is the correct answer.
13
A colourless solution of a compound gives a precipitate with $\mathrm { AgNO } _ { 3 }$ solution but no precipitate with a solution of $\mathrm { Na } _ { 2 } \mathrm { CO } _ { 3 }$. The action of concentrated $\mathrm { H } _ { 2 } \mathrm { SO } _ { 4 }$ on the compound liberates a suffocating reddish brown gas. The compound is:
  1. A $\mathrm { Ba } \left( \mathrm { CH } _ { 3 } \mathrm { COO } \right) _ { 2 }$
  2. B $\mathrm { CaCl } _ { 2 }$
  3. C NaI
  4. D NaBr
Show answer & explanation

Correct answer: D

Pale yellow precipitate is formed.
$\mathrm{NaBr}+\mathrm{AgNO}_{3} \longrightarrow \mathrm{AgBr} \downarrow+\mathrm{NaNO}_{3}$
Therefore, option (4) is the correct answer.
14
The addition of dilute hydrochloric acid to a solution containing the anion ' P ' and the subsequent use of lime water can be used to identify the anion ' P '. What is ' P '?
  1. A Carbonate ion
  2. B Chloride ion
  3. C Iodide ion
  4. D Sulfate ion
Show answer

Correct answer: A

15
Compound $( \mathrm { X } )$, on addition to copper sulphate gives a brown ppt. which turns white on addition of excess of $\mathrm { Na } _ { 2 } \mathrm {S} _ { 2 } \mathrm { O } _ { 3 }$ solution. Compound (X), on addition to $\mathrm { Ag } ^ { + }$ion solution gives a yellow ppt. which is insoluble in $\mathrm { NH } _ { 4 } \mathrm { OH }$. Identify (X).
  1. A $\mathrm { CuI } _ { 2 }$
  2. B KI
  3. C AgI
  4. D NaI
Show answer & explanation

Correct answer: B

X- KI
Reactions:
(i) 2CuSO$_{4}$ + 2KI —→ 2Cu$_{2}$I₂ + K₂SO₄
I₂ + 2Na$_{2}$S$_{2}$O$_{3}$ —→ 2NaI + Na$_{2}$S$_{4}$O$_{6}$
(ii) $\mathrm{Ag}^{+}+\mathrm{KI} \longrightarrow \underset{\text { (yellow ppt.) }}{\mathrm{AgI}+\mathrm{K}^{+}}$
Therefore, option (2) is the correct answer.
16
When N and S both are present in an organic compound, the sodium extract with $\mathrm { FeCl } _ { 3 }$ gives:
  1. A green colour
  2. B blue colour
  3. C yellow colour
  4. D red colour
Show answer

Correct answer: D

17
Which of the following nitrate will give $\mathrm { N } _ { 2 } \mathrm { O }$ on heating?
  1. A $\mathrm { NH } _ { 4 } \mathrm { NO } _ { 3 }$
  2. B $\mathrm { NH } _ { 4 } \mathrm { NO } _ { 2 }$
  3. C $\mathrm { NaNO } _ { 3 }$
  4. D $\mathrm { AgNO } _ { 3 }$
Show answer

Correct answer: A

18
Which of the following ammonium salt will not give acid on heating?
  1. A $\left( \mathrm { NH } _ { 4 } \right) _ { 2 } \mathrm { HPO } _ { 4 }$
  2. B $\left( \mathrm { NH } _ { 4 } \right) _ { 2 } \mathrm { MoO } _ { 4 }$
  3. C $\left( \mathrm { NH } _ { 4 } \right) _ { 2 } \mathrm { SO } _ { 4 }$
  4. D $\mathrm { NH } _ { 4 } \mathrm { Cl }$
Show answer

Correct answer: B

19
Which of the following metal sulphate will give $\mathrm { SO } _ { 2 }$ and $\mathrm { SO } _ { 3 }$ both gaseous product on heating?
  1. A $\mathrm { CuSO } _ { 4 }$
  2. B $\mathrm { FeSO } _ { 4 }$
  3. C $\mathrm { Fe } _ { 2 } \left( \mathrm { SO } _ { 4 } \right) _ { 3 }$
  4. D $\mathrm { CaSO } _ { 4 }$
Show answer

Correct answer: B

20
An unknown salt (S) when heated with dil. $\mathrm { H } _ { 2 } \mathrm { SO } _ { 4 }$ does not evolve brown vapours but with conc. $\mathrm { H } _ { 2 } \mathrm { SO } _ { 4 }$ brown vapours are obtained. The vapours when brought in contact with $\mathrm { AgNO } _ { 3 }$ solution do not give any precipitate. The salt (S) contains:
  1. A $\mathrm { NO } _ { 2 } { } ^ { - }$
  2. B $\mathrm { NO } _ { 3 } { } ^ { - }$
  3. C $\mathrm { I } ^ { - }$
  4. D $\mathrm { Br } ^ { - }$
Show answer & explanation

Correct answer: B

$\mathrm{NO}_{3}{ }^{-}$ion belongs to conc. $\mathrm{H}_{2} \mathrm{SO}_{4}$ group.
Principles Related to Practical Chemistry – NEET-17885 Therefore, option (2) is the correct answer.

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