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201.

A gas that cannot be collected over water is.A. `N_2`B. `O_2`C. `SO_2`D. `PH_3`

Answer» Correct Answer - C
`SO_2` reacts with water to form sulphurous acid, so it cannot be collected over water.
`SO_2 + H_2 O rarr H_2 SO_3`.
Discussion
202.

When excess of ammonia and chlorine react, nitrogen and ammonium chloride are formed. Write the balanced equation and find out how manty ammonium chloride molecules are involved in the balanced equation ?

Answer» Correct Answer - `(6)`
`8 NH_3 (Express) + 3 Cl_2 rarr N_2 + 6 NH_4 Cl`.
Discussion
203.

Ammonia gas can be dried byA. `conc. H_2 SO_4`B. `P_2 O_5`C. `CaCl_2`D. quick lime

Answer» Correct Answer - D
`2 NH_3 overset (H_2 SO_4)rarr (NH_4)_2 SO_4`
`8NH_3 overset (CaCl_2)rarr CaCl_2. 8 NH_3`
`6 NH_3 overset (P_2 O_5)rarr 2 (NH_4)_3 PO_4 +3 H_2 O`
Only `CaO` can be used for drying of ammonia as it does not react with ammonia.
Discussion
204.

On hydrolysis of magnesium nitrate, how many moles of ammonia are produced ?

Answer» Correct Answer - `(2)`
`Mg_3 N_2 + 6 H_2 O rarr 3 Mg(OH)_2 + 2 NH_3`.
Discussion
205.

Ammonia , on reaction with hypochlorite anion, can formA. `NO`B. `NH_4 Cl`C. `N_2 H_4`D. `HNO_2`

Answer» Correct Answer - C
`2 NH_3 OCl^(Ө) rarr H_2 N - NH_2 + Cl^(Ө) + H_2 O`.
Discussion
206.

(a) Sulphur melts form a clear mobile liquid at `199^@ C` but on further heating to `180^@ C`, it becomes viscous. Why ? (b) `SOCl_2` can act as a weak Lewis acid as well as a weak Lewis base. Explain.

Answer» (a) Up to `119^@ C`, sulphur exists as `S_8` molecules which can roll over one another to form a mobile liquid. However, when this liquid is further heated to `180^@ C`, the cleavage of ring structure occurs and zig-zig open chains are formed which get interwound and tangled togther and hence sulphur becomes more viscous.
(b) Like nitrogen in ammonia, sulphur has two lone pair of electrons which it can donate, hence it acts as a weak base.
`SOCl_2` has also empty d-orbitals which can accommodate electron pairs from bases and hence acts as a weak acid.
Discussion
207.

Water is a liquid, while `H_2 S` is a gas at ordinary temperature. Explain.

Answer» In water, there is intermolecular hydrogen bonding, and the molecules are associated. So, it has a higher boiling point and occurs in liquid state.
Whereas, sulphur is less electronegative and cannot participate in hydrogen bonding, so, in hydrogen sulphide there is no hydrogen bonding, and therefore it occurs in gaseous state with low boiling point.
Discussion
208.

What happens when hydrogen sulphide is bubbled through an aqueous solution of sulphur dioxide.

Answer» Sulphur is precipitated
`SO_(2) + 2H_(2) S rarr 3S + 2H_(2) O [SO_(2) rarr S , S^(2-) rarr S]`.
Discussion
209.

(a) Sulphur melts form a clear mobile liquid at `119^@ C` but on further heating to `180^@ C`, it becomes viscous. Why ? (b) `SOCl_2` can act as a weak Lewis acid as well as a weak Lewis base. Explain.

Answer» Sulphur consists of octa-atomic cyclic purkered molecules, At itsmelting point, it becomes a clear liquid, and the rings slip over each other easily. On further heating to a higher temperature, the rings break and long chains are formed. Their network gives rise to a viscous substance.
Discussion
210.

Complete the following equations : (i) `(NH_4)_2 S_2 O_8 + H_2 O + MnSO_4 rarr …..+ …..+ ….` (ii) `S + H_2 SO_4(conc,) overset (Heat)rarr …..+ H_2 O` (iii) `I_2 + SO_2 + H_2 O rarr SO_4^(2-) + …..+ H^(oplus)` (iv) `I_2 + O_3 + H_2 O rarr HIO_3 + .....` (v) `Cr_2 O_7^(2-) + H^(oplus) + SO_2 rarr SO_2^(2-) + H_2 O + .....` (vi) `H_2 S + HNO_3 rarr .... + H_2 O + S`.

Answer» (i) `(NH_(4))_(2) S_(2) O_(8) + MnSO_(4) + 2 H_(2) O rarr (NH_(4))_(2) SO_(4)) + MnO_(2) + 2H_(2) SO_(4)`
(ii) `S + 2 H_(2) SO_(4) rarr 2SO_(2) + 2 H_(2) O`
(iii) `I_(2) + SO_(2) + 2H_(2) O rarr SO_(4)^(2-) + 2 I^(Ө) + 4 H^(oplus)`
(iv) `I_(2) + 5O_(3) + H_(2) O rarr 3HIO_(3) + 5O_(2)`
(v) `Cr_(2) O_(7)^(2-) + 2H^(oplus) + 2 SO_(2) rarr 3SO_(4)^(2-) + H_(2) O + 2 Cr^(3+)`
(vi) `H_(2) S + 2HNO_(3) rarr 2NO_(2) + 2H_(2) O + S ("colloidal")`.
Discussion
211.

Most stable allotropic form of sulphur is rhombic sulphur.

Answer» Correct Answer - T
`D`
Discussion
212.

In the following reaction, `H_2 SO_4` acts as `HCOOH overset (H_2 SO_4) rarr CO + H_2 O`.A. Dehydrating agentB. Oxidising agentC. Reducing agentD. All

Answer» Correct Answer - A
Since `H_2 O` is lost, `H_2 SO_4` is acting as a dehydrating agent
`HCOOH overset (H_2 SO_4)rarr CO + H_2 O`.
Discussion
213.

Conc. `H_2 SO_4` reacts with four moles of `Ag` to give ____ moles of `Ag_2 SO_4`.

Answer» Correct Answer - `(2)`
`2 Ag + underset(Conc.) (2H_(2) SO_(4)) rarr Ag_(2) So_(4) + 2H_(2) O + So_(2)`
`{:(2 "mole",1 "mole",,,),(4 "mole",2 "mole",,,):} `.
Discussion
214.

In the following reaction, `H_2 SO_4` acts as `2 Ag + H_2 SO_5 rarr Ag_2 SO_4 + 2 H_2 O + SO_2`.A. Reducing agentB. Oxidising agentC. Catalytic agentD. Dehydration agent

Answer» Correct Answer - B
`2 Ag + H_2 SO_4 rarr Ag_2SO_4 + 2H_2 O + SO_2`
`Ag rarr Ag^(oplus)`, hence `H_2 SO_4` acts as oxidising agent.
Discussion
215.

From the following information `X + H_2 SO_4 rarr Y` (a colourless and irritating gas) `Y + K_2 Cr_2 O_7 + H_2 SO_4 rarr` green coloured solution Identify the pair `X` and `Y`.A. `Cl^(Ө), HCl`B. `So_3^(2-),SO_2`C. `S^(2-), H_2 S`D. `CO_3^(2-), CO_2`

Answer» Correct Answer - B
`underset((X)) (SO_(3)^(2-)) + 2H^(oplus) rarr underset((Y)) (SO_2) + H_2 O`
`3 SO_2 + K_2 Cr_2 O_7 + H_2 SO_4 rarr K_2 SO_4 + underset("Green coloured solution") (Cr_2(SO_4)_3 + H_2 O)`.
Discussion
216.

Gradual addition of `KI` solution to `Bi(NO_3)_(3)` solution initially produces a dark brown precipitate which dissolves in excess of `KI` to give a clear yellow solution. Write chemical equation for the above reactions.

Answer» `Bi(NO_3)_3` undergoes hydrolysis to form `HNO_3`.
`Bi(NO_3)_3 + 3 H_2 O rarr Bi(OH)_3 + 3 HNO_3`
`HNO_3` reacts will `KI` to liberate `I_2`, which dissolves in excess of `KI` giving clear yellow solution.
`2HNO_3 rarr H_2 O + 2 NO_2 + [O]`
`2 K I + 2HNO_3 + [O] rarr 2 KNO_3 + H_2 O + I_2`
`I_2 + K I rarr K I_3`.
Discussion
217.

The structure of phosphide ion is smaller to that ofA. Nitride ionB. Chloride ionC. Fluoride ionD. Sodium ion

Answer» Correct Answer - B
Phosphide ion, `P^(3-)`. Hence, similar structure with `Cl^(Ө)`.
Discussion
218.

On hydrolysis, of calcium phosphide, how many moles of phosphine are formed ?

Answer» Correct Answer - `(2)`
`Ca_3 P_2 + 3 H_2 O rarr 3 Ca(OH)_2 + 2 PH_3`.
Discussion
219.

When phosphine is bubbled through a solution of nitrate ___ is precipitated.A. SilverB. Silver phosphideC. Silver oxideD. None of these

Answer» Correct Answer - B
`P_4 + 3 AgNO_(3) rarr Ag_3 P + NO_2`.
Discussion
220.

Phosphine, acetylene and ammonia can be formed by treating water withA. `Mg_3 P_2, Al_4 Cl_3, Li_3 N`B. `Ca_3 P_2, CaC_2, Mg_3 N_2`C. `Ca_3 P_2, CaC_2, CaCN_2`D. `Ca_3 P_2, Mg_2 C, NH_4 NO_3`

Answer» Correct Answer - B
`Ca_3 P_2 + 6H_2 O rarr 3 Ca(OH)_2 + 2 PH_3`
`CaC_2 + 2H_2 O rarr Ca(OH)_2 + C_2 H_2`
`Mg_3 N_2 + 6 H_2 O rarr 3 Mg(OH)_2 + 2 NH_3`.
Discussion
221.

Which is the most thermodynamically stable allotropic form of phosphorus ?A. redB. whiteC. blackD. yellow

Answer» Correct Answer - C
Black phosphorus is the most thermodynamically stable from of phosphorous.
Discussion
222.

What happens when `Cl_(2)` reacts with cold dilute solution of sodium hydroxide? (b) Why does chlorine water lose its yellow colour on standing?

Answer» (a) With cold dilute solution of sodium hydroxide , `Cl_(2)` undergoes disproportionation to give a mixture of sodium chloride, `NaCl` and sodium hypochlorite `(NaOCl)`.
`Cl_(2)+2NaOH rarr NaOCl+H_(2)O`
(b) Cholorine water is yellow due to the presence of hypochlorous acid, `HOCl` on standing, `HOCl` being unstable decomposes to form `HCl`. Hence the yellow colour disappears.
`Cl_(2)+H_(2)IO rarr HCl+underset("yellow")(HOCl) rarr underset("colourless")(2HCl)+[O]`.
Discussion
223.

Chlorine water on cooling deposits greenish yellow crystals of formula `CI_(2).XH_(2)O`. What is the value of X ?

Answer» Correct Answer - 8
`CI_(2).8H_(2)O`-Greenish yellow crystals.
Discussion
224.

`PCl_5` has trigonal pyramidal geometry with `sp^3 d` hybridisation in gases and liquid state but in solid state it exist as ionic compound. The hyridisation of `P` and shape of `POCl_3` are.A. `sp^3`, tetrahedralB. `sp^3 d`, distorted tetrahedralC. `sp^3 d`, square planarD. `sp^3`, pyramidal

Answer» Correct Answer - A
`POCl_3` is `sp^3` hybridised with tetrahedral structure.
Discussion