You go to kitchen to boil water. You pour 319 gram of water to a container, and

Question

You go to kitchen to boil water. You pour 319 gram of water to a container, and put the container on a 285 W electric heater. Assume that all the heat from the heater is used to heat the water. The specific heat of water is 4.19 J/g ° C. As always, be accurate to 4 significant digits.

(a) If the temperature of the water is 20.6 ° C before you turn on the heater, how long does it take for the water temperature to reach 100 ° C after you turn on the heater? Provide your answers in minutes.
_____min

(b) After the water temperature reached 100 ° C, if you let the water keep boiling with the heater turn on for 20 minutes, how much water will be left in the container? Latent heat, or the heat of vaporization of water is 2260 J/g. Assume that all the vaporized water is removed from the container.
_____grams

Explanation / Answer

a. Q = m c T

T=Tf-Ti  =100-20.6 =79.4o C

Q= 285 x t

putting in equn

285 x t = 319 x 4.19 x 79.4

t=372.37 sec =6.206 minutes

b.For 20 minutes

Q= 20 x 60 x 285=342000 J

For Q=m L            (L=2260J/g)

m=Q/L = 151.33 g

mass of water left in container = 319 - 151.33= 167.67grams

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