1- How long will it take a 650W microwave oven is used to re-heat a cup of coffe
ID: 2244660 • Letter: 1
Question
1- How long will it take a 650W microwave oven is used to re-heat a cup of coffee containing 220 mL (assume
water) from 20C to 65C. Assume 100% efficiency.
2- What will be the equilibrium temperature when a 355-g block of lead at 95C is placed in a 125-g aluminum
calorimeter cup containing 650 g of water at 6C?
3-. How much energy is required to convert 2 kg of water ice at ?15?C to steam at 150C?
4- An iron rod and a copper rod of the same length and cross-section are attached end-to-end. The copper end is
placed in a furnace at 280C. The iron end is placed in an ice-water bath at 0.0C. Calculate the temperature at
the point where the two rods are joined.
Explanation / Answer
heat requires = mCp dT = 220/1000 x 4200 x (65-20)
Q = 41580 J
heat supply rate = 650 J/s
time = Q / rate of supply
time = 41580 / 650
time = 63.969 s
What will be the equilibrium temperature when a 355-g block of lead at 95C is placed in a 125-g aluminum
calorimeter cup containing 650 g of water at 6C?
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