What is the standard heat of combustion of n heptane gas at 25 degree C if the c

Question

What is the standard heat of combustion of n heptane gas at 25 degree C if the combustion produces water?^2 Determine the heat transfer (in J mol^-1) when water is heated in steady flow process from 25 500 degree C at atmospheric pressure. Show that the entropy change of an ideal gas, with a gas constant R and constant heat capacity undergoing a mechanical reversible work in a closed system from (T_a, P_a) to (T, P) is given expression:^3 [Delta S = integral_r^r C_r^s dT/T - R ln [P/P_0]] One kg of air (M_a = 29 g mol^-1, C_p = 21 J mol^-1 K^-4) is compressed from (25 degree C, 10 bar) to in a frictionless piston cylinder. Assuming that air behaves as an ideal gas, calculate the energy, enthalpy and entropy changes. An inventor claims to have devised a cyclic engine which exchanges heat with reservoirs at 25 250 degree C, and which produces 0.45 kJ of work for each kJ of heat extracted from the hot reservoir claim believable? Why or why not?^3 A heat engine receives 800 kJ of heat from a high temperature source at 900 degree C during a converts 250 kJ of this heat to net work (W) and rejects the remaining quantity of energy temperatures sink at 30 degree C. How much heat is rejected to the low temperatures reservoir?^2 Determine if this heat engine violates the second law of thermodynamics on the basis The Carnot principle, ^2 The Clausius inequality, ^2

Explanation / Answer

Answer 4. I assume the missing image shows some x amount of water being used to produces y J of energy.

So, the balanced chemical equation for heptane is  C7H16 + 11 O2 = 7 CO2 + 8 H2O

so, x moles water produce energy = y J

So, 8 moles of water will produce energy = (y/x) x 8 Joules.

So, standard heat of combustion of heptane = (energy produced by water/ moles of water) x 8 Joules.

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