IIT JEE , AIEEE Forum - Physics , Thermal Physics

pantpranav

It takes 15 minutes to raise a certain amount of water from 0⁰ C to boiling point using a heater. Then it takes 1 hour 20 minutes more to convert all the water into vapour. Find the latent heat of vapourisation of water.

babanbanerjee

Let there be 'm' gm of water.

We know Specific Heat capacity(c) of water is 1cal/gm/deg.cel.

Therefore heat supplied by the heater in 15mins = mct=1*m*(100-0)=100m cals.

So heat supplied per minute = 100m/15 cals=6.67m cals

Therefore the heater can supply in 80mins(1hr 20mins)=6.67*80=534mcals(approx.)

Now again

Q=mL(L=Specific Latent Heat)

So, 534m=mL

Finally hence L=534cals/gm.

Ans.

akhil_o

its direct: heat supplied is equal in unit time,
so L/C*100=t1/t2
so
L=C*80/15*100
=5.33C*100
=533 cals/g

varundhawan5792

is the answer 533.33 cal/g or 2240 J/g

Ask & Discuss Questions with Community & Experts