Answer to Question #101439 in Physical Chemistry for Abhishek

Question

a) What is the value of density of mercury non-SI units? Convert and express this quantity in SI unit.


b) List the factors on which the amount of a gas adsorbed on a solid depends.

Answer 1

1.)

The density of mercury is 13.6 grams per cubic centimeter.

converting this into SI system:

$1 m³ = 10^6 cm^3 \\ Converting: \\ 13.6g/cm³ *(1,000,000 cm³/ 1 m³) = 13,600,000 g/ m³ \\ \\\\ \\13,600,000 g/m³ * (1 kg / 1,000g) = 13,600 kg / m³ \\ \\ Answer \ is =\\13,600 kg/m³, or 1.36 x 10^4 kg/m³\\$

2.)

The factors on which the amount of a gas adsorbed on a solid depends are:

(i)Nature of adsorbent

The adsorption of the gas depends on the nature of the adsorbent. A gas can be adsorbed on different absorbent surfaces in different amounts. For example, Hydrogen is weakly adsorbed on the alumina surface whereas it is strongly adsorbed on the nickel surface under certain conditions.

(ii)Surface area

When we increase the surface area of the adsorbent there is an increase in the adsorption of gases. This is because when we increase the surface area there is more number of adsorbing sites. So finely divided solids and some porous substances are good adsorbents.

(iii) Nature of the gas

In general, if a gas is more liquefiable it will be more easily absorbed. For example, Gases like NH3, HCl, Cl2, CO2, which can be liquefied easily are more readily adsorbed on the solids surface rather than permanent gases like O2, H2, etc.

(iv) Exothermic nature

The heat of adsorption can be defined as the energy liberated when 1 g mol of a gas is liberated on a solid surface. When the temperature is increased the kinetic energy of the gas molecules also increases which results in more number of collisions between the molecules and the surface.

(v) Pressure

On the solid surface, there is a fixed number of adsorption sites where gas molecules can be adsorbed. Initially when the pressure has increased the rate of adsorption increases due to an increase in the gas molecules striking on the surface. Thus an increase in the pressure increases the rate of adsorption linearly. But after sometime, it will reach a point when the pressure has no effect on the rate of adsorption as the number of adsorption sites is fixed and no more adsorption can happen in those sites. Hence at that point, the extent of adsorption will be independent of the pressure.