The correct option is D 375 gm
Given that,
Mass of liquid 2 (m2)=100 gm
Specific heat of liquid 1 (c1)=0.2 cal/g∘C
Specific heat of liquid 2 (c2)=0.5 cal/g∘C
Temperature of liquid 1 (θ1)=40∘C
Temperature of liquid 2 (θ2)=20∘C
Let m1 be the required mass of liquid 1.
When both the liquids are mixed, heat transfers between them until they reach thermal equilibrium at θ=32∘C
Using principle of calorimetry, we can say that.
Heat lost by liquid 1 = Heat gained by liquid 2
i.e m1c1(θ1−θ)=m2c2(θ−θ2)
Thus, temperature of mixture can be written as,
θ=m1c1θ1+m2c2θ2m1c1+m2c2
⇒32=m1×0.2×40+100×0.5×20m1×0.2+100×0.5
⇒8m1+1000=6.4m1+1600
⇒1.6m1=600
⇒m1=375 g
Thus, option (d) is the correct answer.