The correct order of the thermal stability of hydrogen halides(H–X) is

HI > HCl < HF > HBr
HCl< HF > HBr < HI
HF > HCl >HBr > HI
HI < HBr > HCl

Solution

The H–X bond strength decreases from HF to HI. i.e.HF > HCl > HBr > HI. Thus HF is most stable while HI is least stable. The decreasing stability of the hydrogen halide is also reflected in the values of dissociation energy of the H–X bond

P₂O₅ is an anhydride of

HPO₃
H₃PO₄
H₃PO₃
H₂P₂O₇

Solution

H₃PO₄

P₂O₅ exists as dimer (P₄O₁₀)

P₄O₁₀ + 6H₂O → 4H₃PO₄

Which of the following is the best description for the behaviour of bromine in the reaction given below ?

H²O + Br₂ → HOBr + HBr

Proton acceptor only
Both oxidized and reduced
Oxidized only
Reduced only

Solution

\(H_{2}O+\overset{0}{Br_{2}}\rightarrow \overset{+1}{HOBr}+ \overset{-1}{HBr}\)

Thus here oxidation number of Br increases from 0 to+1 and also decreases from 0 to –1. Thus it is oxidised as well as reduced.

A one litre flask is full of brown bromine vapours. The intensity of brown colour of vapours will not decrease appreciably on adding to the flask some

pieces of marble
animal charcoal powder
carbon tetrachloride
carbon disulphide

Solution

Due to absence of reaction between marble and bromine.

Which one is the correct order of the size of iodine species?

I >I⁺> I^-
I > I^-> I⁺
I⁺ > I^-> I
I^- > I > I⁺

Solution

We know that positive ion is always smaller and negative ion is always larger than the corresponding atom. Therefore the correct order of the size is

I^- > I > I⁺

Ammonia and sodium hypochlorite reacts to produce

NH₂OH₂
NH₂NH₂
N₂
NO

Solution

NH₃ + NaOCl \(\overset{fast}{\rightarrow}\) NH₂ + NaOH

2NH₃ + NH₂Cl → NH₂NH₂ + NH₄Cl

Which one of the following oxides of chlorine is obtained by passing dry chlorine over silver chlorate at 90°C ?

Cl₂O
ClO₃
ClO₂
ClO₄

Solution

2AgClO₃ + Cl₂(dry)\(\overset{90^{\circ}C}{\rightarrow}\) 2AgCl + 2ClO₂ + O₂

A solution of potassium bromide is treated with each of the following. Which one would liberate bromine ?

Hydrogen iodide
Sulphur dioxide
Chlorine
Iodine

Solution

A stronger oxidising agent (Cl²) displaces a weaker oxidising agent (Br₂) from its salt solution.

2KBr + Cl₂ → 2KCl Br₂

Which of the following species has four lone pairs of electrons?

I
O^-
Cl^-
He

Solution

In the manufacture of bromine from sea water, the mother liquor containing bromides is treated with

carbon dioxide
chlorine
iodine
sulphur dioxide

Solution

Bromide in the mother liquor is oxidised to Br₂ by Cl₂
which is a stronger oxidising agent.

2Br^- + Cl₂ → Br₂ + 2Cl^-

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