A certain amount of ice is supplied heat at a constant rate for 7 minutes. For the first one minute the temperature rises uniformly with time. Then, it remains constant for the next 4 minute and again the temperature rises at uniform rate for the last two minutes. Calculate the final temperature at the end of seven minutes.
(Given, L of ice `= 336 xx (10^3) J//kg` and specific heat of water `= 4200 J//kg.K`).

Options

A. The initial temperature of ice is `-30^(@)C`.
B. The final temperature at the end of `7` min is `40^(@)C`.
C. The final temperature at the end of `7` min at `30^(@)C`
D. Between `t=1min` to `t=5min` it does not changes its phase.

Explanation

Let `m` be the mass of ice and `q` the rate by which heat is supplied, then
`qxx1=m(0.5)(-theta_(i))`…..(`1`)
`qxx4=mxx80`…..(`2`)
`qxx2=m I.theta_(f)`…..(`3`)
From these equation
`Q_(f)=40^(@)C`
`Q_(i)= -40^(@)C`