Number of correct statements is/are ‘a’ and incorrect statements ‘b’. Then a x b is 

1) n – Hexane and n – Heptane form ideal solution
2) Bromo ethane and Chloro ethane form ideal solution 
3) Benzene and Toulene form ideal solution
4) ethanol and acetone form non ideal solution with –ve deviation
5) Carbondisulphide and acetone form non ideal solution with +ve deviation
6) phenol and aniline form non ideal solution with –ve deviation
7) chloroform and acetone form non ideal solution with +ve deviation
8) Van’t hoff factor (i) =  $\frac{Abnormalmolarmass}{normalmolarmass}$