NEET

Solution

For a Carnot engine, the source is at 500 K and the sink at 300 K. What is efficiency of this engine :

Solution

Efficiency of engine = \(\frac{T_{1} - T_{2}}{T_{1}}\) =
\(\frac{200}{500}\) = 0.4.

Enthalpy of solution of NaOH (solid) in water is – 41.6kJ mol^-1. When NaOH is dissolved in water, the temperature of water :

increases
decreases
does not change
fluctuates indefinitely

Solution

Dissolution of NaOH in water is an exothermic reaction as indicated by negative value of enthalpy leading to increase in temperature.

Solution

Standard heat of formation of a substance is amount of heat evolved or absorbed when one mole of substance is formed from its elements in their standard states. Since standard state of carbon and hydrogen are graphite and gaseous H₂ respectively. Hence standard heat of formation of methane is given by

C(graphite) + 2H₂(g) ⟶ CH₄(g)

The enthalpy of hydrogenation of cyclohexene is – 119.5 kJ mol^-1. If resonance energy of benzene is –150.4 kJ mol^-1,its enthalpy of hydrogenation would be