When gasoline burns in a car engine, the heat released causes the products CO_2

Question

When gasoline burns in a car engine, the heat released causes the products CO_2 and to expand, which pushes the pistons outward. Excess heat is removed by the car's radiator. If the expanding gases do 451 J of work on the pistons the system releases 325 J to the surroundings as heat, calculate the change in energy (delta E) in kJ and kcal. (delta E = w + q) What is the sign of work? What is the sign of heat? What is the change in energy (delta E) in J? What is the change in energy (delta E) in kJ? What is the change in energy (delta E) in kcal? Determine the exothermic and endothermic for the following processing based on the Enthalpy diagrams. Is the above processing A an exothermic or endothermic? Is the above processing B an exothermic or endothermic?

Explanation / Answer

work done is possitive if work is done on the system and negative if the work is done by the system

q is possitive if heat is added to the system and is negative if heat is removed from the system

here work is done by the system hence sign of work done is negative Answer

heat is released from the system to sorroundings so heat is negative Answer

Change in internal energy = Q + W = - 325 J - 451 J = - 776 J Answer

In KJ we have to multiply by 10-3 in KJ = - 0.776 KJ Answer

in kcal we have to divide in KJ by 4.184 in kcal = - 0.1855 kcal Answer

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