Question

# It takes 15 minutes to rise a certain amount of water from $$0^oC$$ to boiling point using a heater. Then it takes 1 hour and 20 minutes to convert all the water into vapour. Then the latent heat of vapourization of water is:

A
525 cal
B
540 cal
C
533 cal
D
513 cal

Solution

## The correct option is C 533 calLet the power delivered by the heater = $$P$$.Heat supplied in $$15$$ minutes = $$15P$$ = $$Q_{1}$$Heat supplied in $$1$$ hour and $$20$$ minutes = $$80P$$ = $$Q_{2}$$$$Q_{1} = mc\Delta T = m(1)(100) = 100m$$$$Q_{2} = mL$$ L is the latent heat of vaporization.i.e. dividing $$Q_{1} \ and \ Q_{2}$$$$\dfrac{15}{80} = \dfrac{100}{L}$$i.e. $$L = 533.33$$ cal. Hence answer is option C.Physics

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