A molecule ‘M’ associates in a given solvent according to the equation M⇌(M)n for a certain concentration of ‘M’ , the van't hoff factor was found to be 0.9 and the fraction of associated molecules was 0.2, the value of n is

Let the degree of association be α                       M⇌(M)n  Initially           1       0        After time t  1-α    αnTotal moles after association = 1-α+αn=1+1n-1α                        i=moles after associationinitial moles=1+1n-1α1 i-1=1n-1; i=1-α+αn; By substituting   i=0.9 , α=0.2  we get        n=2