Van't Hoff value for
NH3
Nitric acid
Sulphuric acid.
Sodium carbonate
Alcl3

Dear student, 
Van't Hoff factor is determined by the no. of ions formed per molecule. 
NH₃ Van't Hoff factor is 1 as it doesn't dissociate. 
Nitric acid - 2 ( HNO₃→H⁺ + NO₃^-) 
Sulphuric acid - 3 (H₂SO₄ → 2H⁺ + SO₄^2-) 
Sodium carbonate- 3   ( Na₂CO₃ → 2Na⁺ + CO₃^2-) 
Aluminium chloride - 4 ( AlCl₃ → Al³⁺ + 3Cl^-) 
Regards