We have d = $\frac{\mathrm{PM}}{\mathrm{RT}}$

or $\frac{{\mathrm{d}}_1{\mathrm{T}}_1}{{\mathrm{P}}_1} = \frac{{\mathrm{d}}_2{\mathrm{T}}_2}{{\mathrm{P}}_2}$

According to the equation,

d₁ = 2.86 kg m^-3 , d₂ = ?

T₁ = 273K

T₂ = 819 + 273 = 1092 K

P₁ = 1 atm

P₂ = 2 atm

$\therefore$ $\frac{2.86 \times 273}{1} = \frac{{\mathrm{d}}_2 \times 1092}{2}$

or d₂ = $\frac{2 \times 2.86 \times 273}{1092}$

        = 1.43 kg m^-3

Molar mass of water = 18 g/mol

      Density of water = 1 g/mol

$\because$ 1 l = 1000mL

$\therefore$ 1l of water = 1000 gm

Molecules = $\frac{\mathrm{mass}}{\mathrm{molar} \mathrm{mass}} = \frac{1000 \mathrm{g}}{18 \mathrm{g}/\mathrm{mol}}$

             = 55.56 mol water

Molarity = $\frac{55.56 \mathrm{mol}}{1 \mathrm{L}}$ = 55.56 M

Zinc is that metal, which gives white precipitate when H₂S gas is passed in the ammonical solution of its salt.

In ethylene H₂C = CH₂, the C - C bond distance is 1.34 Å, therefore, the $\mathrm{\pi }$ electrons of the double bond are easily exposed to the reactant (electrophiles) which readily react. In acetylene molecule HC $\equiv$ CH, although there are two $\mathrm{\pi }$ bonds but these electrons are not exposed to the attacking reagents due to small bond distance of C $\equiv$ C bond (1.20 Å). A catalyst mercuric ion is therefore needed in reactions with actylene.

Noble gases have fully filled valence shell electronic configuration. Therefore, it represents ns²np⁶ electronic configuration.

The P-H bond in H₃PO₃ is not ionisable and do not play any role in its basicity. Only those atoms which are attached to O in P-OH form are ionisable and are responsible for the basicity. Thus, H₃PO₃ is dibasic as it has two P-OH bond.

We know that 1 gm equivalent weight of NaOH = 40 gm

$\therefore$ 40 gm of NaOH = 1 gm equivalent of NaOH

$\therefore$ 0.275 gm of NaOH = $\frac{1}{40} \times$ 0.275 eq.

                                = $\frac{1}{40} \times 0.275 \times 1000$

                                = 6.88 meq

$\because$                    N₁V₁ = N₂V₂

                N₁ $\times$ 35.4 = 6.88 ( $\because$ meq = NV)

                           N₁ = 0.194

Therefore, 0.194 N is the normality of HCl. 

amu represents atomic mass unit. It is used in place of unified mass unit.

1 amu = 1 Avogram = 1 Aston = 1 Dalton

1 amu = $\frac{1}{12} \times$ mass of C-12 atom

          = $\frac{1}{12} \times 1.9924 \times {10}^{-23} \mathrm{g}$

          = 1.66 $\times$ 10^-24 g 

          = 1.66 $\times$ 10^-27 g

Therefore, the correct option is d.

The melting and boiling point of noble gases are low because of the presence of weak Van der Waals forces or weak London dispersion forces between the atoms of the noble gases.

The molecule having largest dipole moment is CHCl₃.