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Question: Answered & Verified by Expert
A thermos flask contains $250 \mathrm{~g}$ of coffee at $90^{\circ} \mathrm{C}$. To this $20 \mathrm{~g}$ of milk at $5^{\circ} \mathrm{C}$ is added. After equilibrium is established, the temperature of the liquid is
(Assume no heat loss to the thermos bottle. Take specific heat of coffee and milk as $\left.1.00 \mathrm{cal} / \mathrm{g}^{\circ} \mathrm{C}\right)$
PhysicsThermal Properties of MatterTS EAMCETTS EAMCET 2015
Options:
  • A $3.23^{\circ} \mathrm{C}$
  • B $3.15^{\circ} \mathrm{C}$
  • C $83.7^{\circ} \mathrm{C}$
  • D $37.8^{\circ} \mathrm{C}$
Solution:
2685 Upvotes Verified Answer
The correct answer is: $83.7^{\circ} \mathrm{C}$
Let after getting equilibrium stage final temperature is $T$.
Then, according to loss of calorimetry
Heat loss $=$ Heat gain
$$
\begin{aligned}
\Rightarrow(250)(1)(90-T) & =20(1)(T-5) \\
\Rightarrow \quad T & =83.7^{\circ} \mathrm{C}
\end{aligned}
$$

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