electric heater rated 2.5kw is being used to boil a liquid.1.2kg of the liquid evaporates in 30mins.calc the latent heat of veporisation?

Heat gained by the liquid = Heat supplied by the heater
(1.2 × 1000 g) × Lv = (2.5 × 1000 J/s) × (30 × 60 s)

Latent heat of vaporization, Lv
= (2.5 × 1000) × (30 × 60) / (1.2 × 1000)
= 3750 J/g
= 3.75 kJ/g