Boyles Law Viva Questions

Boyles Law Viva Questions and Answers

(i) What is the S.I. unit of pressure?

Ans: N.m^-2

(ii) Atmospheric pressure at sea level is 0.76 m of mercury. What is the pressure in N.m^-2? Density of mercury = 13.6 x 10⁵ kg/m³.

Ans: P = hdg = 0.76 x 13.6 x 10⁵ x 9.8 = 1.013 x 10⁵ Nm^-2or one Atmosphere.

(iii) State Boyles law

Ans: At constant temperature, the volume of a given mass of gas varies inversely as its pressure ie, v ∝ 1/p or, pv = constant

(iv) What is gas constant? It is a universal constant for all gases at S.T.P.

Ans: R =PV/T = 1.01 x 10⁵ x 22.4 x 10^-3/273 = 8.3 J/mol/k.

(v) What are the limitations of Boyles law?

Ans: It does not hold good for high pressures and low temperatures. It is also not true for saturated vapour.

(vi) What is critical temperature?

Ans: It is the temperature above which a gas cannot be liquefied by applying pressure.

(vii) Do all gases obey Boyles law

Ans: Real gases do not obey Boyles law. So called permanent gases like O₂, H₂, etc obey Bolyle's law at ordinary temperature and pressure.

(viii) What is an ideal gas?

Ans: A gas which obeys Boyles law and Charles law is called perfect gas or ideal gas. Intermolecular force is zero

(ix) Why do we use mercury for measuring pressure

Ans: It and does not wet glass. Hence a small column of liquid is enough

(x) What is the shape of P.V. diagram?

Ans: It is a part of a hyperbola.

(xi) Aim of Boyles Law Experiment?

Ans: To study the variation of volume of a sample of air with its pressure at constant temperature using Boyle's law apparatus.

(xii) Apparatus of Boyles Law Experiment?

Ans: Boyle's law apparatus Boyle's law apparatus consists of a uniform glass tube AB closed at one end. It is fixed vertically on a stand with its open end downwards. The tube is connected to a reservoir R by means of a rubber tube. The reservoir contains mercury. The glass tube AB contains pure dry air. The reservoir can be raised or lowered and can be fixed at any position. Thus the pressure and volume of air inside the glass tube can be varied. A scale is fixed between AB and the reservoir.

(xiii) Theory of Boyles Law Experiment?

Ans: According to Boyle's law, at constant temperature, volume V of a given mass of gas (air) is inversely proportional to its pressure P.

i.e., P ∝ 1/V

Therefore, PV = a constant.

Since the glass tube is uniform, V ∝ l, the length of the air column in the glass tube.

P ∝ (1/l); ie, Pl = a constant