What is the efficiency of a heat engine if the heat energy extracted from the source is 950 J and the engine rejects 570 J of heat to the sink at the end of the cycle?

A body of mass 2 kg and Cp = 1.00 kJ/kg·K is at 600 K. If the atmosphere is at 300 K, the maximum work obtainable from the body till it comes to equilibrium with the atmosphere is:

The magnitude of work done when 1 mole of zinc dissolves completely in aqueous HCl in an open beaker at 27°C is (take R = 8.314 J K−1 mol−1):