At 298 K, liquid A (solute) forms an ideal solution with liquid B (solvent). The following graph is obtained for this solution.
Identify the correct statements about this graph:
I) x-axis represents the mole fraction of A
II) Point Z represents the vapour pressure of pure solvent
III) x-axis represents the mole fraction of B
Which of the following properties will change when system containing solution 1 will become solution 2 ? 
Find the variance of the following frequency distribution:
| Class Interval | ||||
| 0--4 | 4--8 | 8--12 | 12--16 | |
| Frequency | 1 | 2 | 2 | 1 |