Anonymous
Anonymous asked in Science & MathematicsPhysics · 1 month ago

# I don't understand how to do this question?

A 50 g block of copper (20°C) is placed inside 90 g of an unknown liquid (75°C) . If the final temperature of the

mixture was 25°C, what was the specific heat capacity of the unknown liquid?

Relevance

specific heat capacity of copper cc = 390 joule/(kg*K)

specific heat capacity of unknown liquid  cℓ = ??? joule/(kg*K)

Energy conservation shall apply

(mc*cc*Tc+mℓ *cℓ *Tℓ) = 25*( (mc*cc+mℓ *cℓ )

(0.05*390*20+0.090*cℓ *75) = 25(0.05*390+0.090*cℓ )

cℓ *0.090*(75-25) = 0.05*390*(25-20)

cℓ   =  0.05*390*(25-20) / (0.090*(75-25)) = 21.7 joule/(kg*K)

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• the answer says its 21.7 J / kg °C

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• Specific Heat of copper = 0.385 J/g°C

50(0.385)(25-20) = 90c(75-25)

--->c = 0.0214 J/g°C

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• energy to warm the Cu is 377 J/kgC x 0.05 kg x (25–20) = 94.25 J

energy to cool the unknown is the same

E = 94.25 J = SH x 0.09 kg x (75–25) = 4.5•SH

SG = 94.25/4.5 = 20.9 J/kgCspecific heat Copper is 377 J/kgC

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