9. In an experiment, a 0.300-kg piece of ceramic superconducting material at 27
ID: 2036349 • Letter: 9
Question
9. In an experiment, a 0.300-kg piece of ceramic superconducting material at 27 °C is placed in liquid nitrogen at its boiling point (-195.8 °C) to cool The nitrogen is in a perfectly insulated flask that allows the gaseous N2 to escape immediately. How much mass of liquid nitrogen will be boiled away? (Take the specific heat of the ceramic material to be the same as that of glass.) grams 10. A 0.500-kg of water is initially at temperature of 38 °C. How much heat is required to boil away one-half the mass of the water?Explanation / Answer
for ceramic, C = 850 J / kg K
Energy released during cooling,
Q = m C deltaT = 0.300 x 850 x (27 + 195.8)
Q = 56814 J
for nitrogen, Lv = 200 x 10^3 J / kg
and Q = m Lv
56814 = m (200 x 10^3)
m = 0.284 kg Or 284 grams
10. Q = m C deltat + m Lv
Q = (0.500 / 2) (4184) (100 - 28) + (0.500/2)(2230 x 10^3)
Q = 632812 J Or 6.33 x 10^5 J
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