Heat and Thermodynamics 1 Question 5

5. A metal ball of mass 0.1kg is heated upto 500C and dropped into a vessel of heat capacity 800JK1 and containing 0.5 kg water. The initial temperature of water and vessel is 30C. What is the approximate percentage increment in the temperature of the water? [Take, specific heat capacities of water and metal are respectively 4200Jkg1K1 and 400Jkg1K1 ]

(2019 Main, 11 Jan II)

(a) 25

(b) 15

(c) 30

(d) 20

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Solution:

  1. Using heat lost or gained without change in state is ΔQ=msΔT, where s is specific heat capacity and T= change in temperature

Let final temperature of ball be T.

Then heat lost by ball is,

ΔQ=0.1×400(500T)

This lost heat by ball is gained by water and vessel and given as

Heat gained by water,

ΔQ1=0.5×4200(T30)

and heat gained by vessel is

ΔQ2= heat capacity ×ΔT=800×(T30)

According to principle of calorimetry, total heat lost = total heat gained

0.1×400(500T)=0.5×4200(T30)+800(T30)

(500T)=(2100+800)(T30)40500T=72.5(T30)500+217.5=72.5T or T=36.39K

So, percentage increment in temperature of water



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