10-1.Thermometry, Thermal Expansion and Calorimetry
medium

$250\,gm$ of water and an equal volume of alcohol of mass $200\,gm$ are placed successively in the same calorimeter and cools from $60^{\circ}\,C$ to $55^{\circ}\,C$ in $130\,sec$ and $67 sec$ respectively. If the water equivalent of the calorimeter is $10\,gm$. , then the specific heat of alcohol in cal/gm $cal / gm ^{\circ}\,C$ is

A

$1.30$

B

$0.67$

C

$0.62$

D

$0.985$

Solution

(c)

Mass of water $=250 g$

Mass of alcohol $=200 g$

Water equivalent of calorimeter, $W=10 g$

Fall of temperature $=60-55=5^{\circ} C$

Time taken by water to cool $=130 s$

Time taken by alcohol to $cool =67 s$

Heat lost by water and colorimeter

$=(250+10) 5=260 \times 5=1300 cal$

Rate of loss of heat $=\frac{1300}{130}=10 cal / s$

Heat lost by alcohol and calorimeter $=(200 s+10) 5$

Rate of loss of heat $=\frac{(200 s +10) 5}{67} cal / s$

Heat lost by alcohol and calorimeter $=(200 s+10) 5$

Rate of loss of heat $=\frac{(200 s +10) 5}{67} cal / s$

Rates of loss of heat in the two cases are equal

$\frac{(200 s+10) 5}{67}=10$

$s=0.62\; cal / g^{\circ} C$

Standard 11
Physics

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