About 86% of the world\'s electrical energy is produced by using steam turbines,

Question

About 86% of the world's electrical energy is produced by using steam turbines, a form of heat engine. In his analysis of an ideal heat engine, Sadi Carnot concluded that the maximum possible efficiency is defined by the total work that could be done by the engine, divided by the quantity of heat available to do the work (for example from hot steam produced by combustion of a fuel such as coal or methane).

efficiency=w/q100

The fuel in high-efficiency natural gas vehicles consists primarily of methane CH4

Part A

How much heat is produced in burning 6 mol of CH4 under standard conditions if reactants and products are brought to 298 K and H2O(l) is formed?

Express your answer using four significant figures.

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Part B

What is the maximum amount of useful work that can be accomplished under standard conditions by this system?

Express your answer using four significant figures.

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Part C

What is the maximum efficiency of a heat engine burning natural gas?

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Explanation / Answer

The combustion reaction can be written as CH4+2O2----> CO2+ 2H2O

Enthalpychange= sum of enthalpy change of prodcts- sum of enthalpy change of reactants=

-395.8 ( Ethanlpy change of CO2)+2*(-241.8) (Enthalpy change of H2O) - { -(74.6) ( enthalpy change of CH4+2*0(enthalpy change of oxygen) =-802.5 Kj/mol

when 6 moles of CH4 is burnt, heat generated= 6*802.5=4815 Kj

Part B. The effficiency of CH4 based engines is 40%.( Ref : https://en.wikipedia.org/wiki/Gas_engine)

Based on this useful work= 4815*0.4= 1926 Kj

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