Exercise 7.107 - Enhanced with Feedback Part A Some of the butane, C4H(g), n a 4

Question

Exercise 7.107 - Enhanced with Feedback Part A Some of the butane, C4H(g), n a 400.0 L cylinder at 31 C is withdrawna As a result, the pressure of the gas in the cylinder falls from 2.30 atn to 1.15 atm. The liberated heat is used to raise the temperature of 133.0L of water in a heater from 31 C to 64 C Assume that the combustion products are CO2(g) and H2O() exclusively, and determine the efficiency of the water heater. (That is, what percent of the heat of combustion was absorbed by the water?) a constant pressure in an excess of air 0? efficiency = Submit My Answers Give Up

Explanation / Answer

Q = m*C*(Tf-Ti)

Q = 133*4.184*(64-31)

Q = 18363.576 kJ

then

Total heat

moles of C4H10

PV = nRT

n = PV/(RT) = 2.3*400/(31+273)/0.082 = 36.906

Hcomb = -2877.5

Qcombustion = -2877.5 * 36.906 = 106197.015 kJ

%eff = Qwater/Qcomb * 100% = 18363.576 /106197.015*100 = 17.3%

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