Question

hey guys
can someone explain to me why the answer is B in question 9? see attachment
thanks :)

Answer 1

The graph shows the effect of salt present in solvent on vapor pressure :)
as the amount of ions in solvent increases the the vapor pressure drops or it shows vapor pressure at higher temperature as shown in the graph.
1 mole of NaCl produces 1 mole of Na+ and 1 mole of Cl-
1 mole of MgCl2 produces 1 mole of Mg and 2 mole of Cl-
hence total no of ions in case of Mg Cl2 are 3 compared to Nacl where only 2 ions are present hence
1 curve is pure solvent
2 curve for NaCl and
3 curve for the MgCl2