A. How much energy would you have to add to get 0.5 kg of ethyl alcohol from an

Question

A. How much energy would you have to add to get 0.5 kg of ethyl alcohol from an ice at temperature of -114 C to a liquid temperature at 50 C? Use these facts about ethyl alcohol: it goes from an ice to a liquid at -114 C, its Lf= 1.04 x 10^5 j/kg and its specific heat is 2440 j/kg C.

B. A star is observed that has exactly the same surface temperature as the sun, 5800 K, but the measured power output is 100 x of that of the sun. If R = 6.96 x 10^8, what is the radius of the start? ( e=1 for stars and the area of a sphere is A= 4(3.14)R^2

Explanation / Answer

a) q = m L + M c dT = 0.5*1.04E5 + 0.5*2440*(50 + 114)=252080 J

b) P = sigma A e T^4

so if 100 times the P but t the same that means A is 100 times bigger

so R star = 10*Rsun = 69.6E8

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