ULLI
c. O
UU
P.
(4) 500 mL of water at 20°C is mixed with 1 litre of water at 60 °C,
then what will be the temperature of the mixture ?
A. 80 °C B. More than 60°C but less than 80 °C
C. 40 °C D. More than 20°C but less than 60 °C
Answers
Answer:
Explanation:
Correct option is
D
between 30C and 50C
Let the first volume of water be V1. Let the second volume of water be V2. Let the initial temperature of the first volume of water be θ1. Let the initial temperature of the second volume of water be θ2.
Let the energy required to heat a unit volume of water by unit temperature by C.
So, if the final temperature is θfinal, we have
heat gained by the first volume of water
=V
1
×C×(θ
final
−θ
1
)
and
heat lost by the second volume of water
=V
2
×C×(θ
2
−θ
final
).
By the law of conservation of energy,
heat lost = heat gained
∴V
1
×C×(θ
final
−θ
1
)=V
2
×C×(θ
2
−θ
final
)
∴V
1
θ
final
−V
1
θ
1
=V
2
θ
2
−V
2
θ
final
∴θ
final
=V
1
θ
1
+V
2
θ
2
V
1
+V
2
Substituting the given values,
θ
final
=
2
30+50
=40
∘
C.
The answer is option D