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WAEC Physics 2024 Paper

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Question : 42

Total: 50

A non-conducting vessel contains a liquid of mass 70 g at 25º C. Another 70.0g of the same liquid at 35ºC is quickly poured into the vessel. Determine the final temperature of the mixture

15ºC
20ºC
30ºC
40ºC

Solution:

Heat gained by 25º C body = Heat lost by 35º C body

M $\_c$ c $\delta$ $\theta$ = M $\_h$ c $\delta$ $\theta$

70 x c x (f - 25) = 70 x c x (35 - f)

where f = final temperature

f - 25 = 35 - f (f and 70 cancel out)

2f = 35 + 25 = 60

f = $\; \frac{60}{2}$ = 30ºC

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