Two 50-g ice cubes at -15 degree C are placed into 0.200-kg of water at 25 degre

Question

Two 50-g ice cubes at -15 degree C are placed into 0.200-kg of water at 25 degree C. Given the sp ht of ice 2.05 kJ/kg. degree C, find the final temperature of the mixture. a. none b. 20 degree C c. -12.4 degree C d.10 degree C e. 12.4 degree C While the outdoor temperature on a winter day is -15 degree C and the indoor temperature is 22 degree C, find the rate of heat loss through a 0.32-cm thick glass windowpane that measures 20.0 cm by 15.0 cm. (thermal conductivity of glass is 0.63 W/(m.K). a. 220 kcal b. 220 W c. none d. Both (a) and (b) e. 220 J/s

Explanation / Answer

Q4 ans

Given that

mass m1=0.05 kg

temperature T1=-15 C

temperature T2=25 c

mass m2=0.2 kg

basing on the concept of calorometry

now we find the mixed temperature

The finial temperature T=m1s1T1+m2s2T2/m1s1+m2s2

=0.05*2050*-15+0.2*4200*25/0.05*2050+0.2*4200

=-1537.5+21000/102.5+840

=19462.5/942.5

=20.C

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Q5 ans

Given that

area A=20*15=300*10^-4 m^2

thickness L=0.0032 m

temperature difference =T1-T2=22+15=37 c

thermal conductivity K=0.63 W/(m.K)

now we find the power

power =KA[T1-T2]/L

=0.63*3*10^-2*37/0.0032

=218.5 W

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