Two gases A and B which react according to the equation aAg+bB (g) to give two gases C and D are taken (amount not known) in an Eudiometer tube (operating at a constant Pressure and temperature) to cause the above. cC + dD (g) If on causing the reaction there is no volume change observed then which of the following statement is/are correct. (a) (a + b) = (c + d) (b) average molecular mass may increase or decrease if either of A or B is present in limited amount. (c) Vapour Density of the mixture will remain same throughout the course of reaction. (d) Total moles of all the component of mixture will change.