Question

the ratio of the number of molecules in 4 gram of hydrogen gas to the number of molecules in 5.6 litre of oxygen at standard temperature and pressure is

Answer 1

Num. 5. The volume of gases A, B, C and D are in the ratio, 1 : 2 : 2 : 4 under the same conditions of temperature and pressure: 
(i) Which sample of gas contains the maximum number of molecules? 
(ii) If the temperature and the pressure of gas A are kept constant, then what will happen to the volume of A when the number of molecules is doubled? 
(iii) If this ratio of gas volumes refers to the reactants and products of a reaction, which gas law is being observed? 
(iv) If the volume of A is actually 5.6 dm3 at S. T. P. calculate the number of molecules in the actual volume of D, at S. T. P. (Avogadro’s Number is 6 × 1023). 
(v) Using your answer from (iv) state the mass of D if the gas is Di-nitrogen dioxide (N2O). (N = 14; O = 16).

Sol : - (i) The sample D. (ii) Volume of A will get doubled. (iii) Gay Lussac’s Law. 
(iv) 
Gases A D 
Volumes 1 : 4 
5.6 dm3 4 × 5.6 dm3 at S. T. P. 
= 22.4 dm3 (Molar volume) 
= 6 × 1023 molecules. 
(v) 6 × 1023 molecules is Avogadro’s number of molecules contained in 1 gram mole of the substance. If gas d is N2O then , 
1 gram mole of N2O = 2 × 14 + 16 = 44g.