Abstract This paper analyzed three typical examples of physical chemistry that students ensily confuse or make mistakes. The first question:Comparison of temperature and pressure when the ideal gas went through two ways of adiabatic reversible expansion and adiabatic irreversible expansion from the same initial state to the final state with the same volume.The answer to this question can not be obtained by the maximum power principle because of the different final state, but the principle of entropy increasing was more scientific.The second question:The problem about the calculation of the rate constant and half-life of the second order reaction 2A→B. The third question:Overheating phenomenon existed when the water distilled, how much degree was needed if the minute bubbles of a diameter was steamed out? We explained this question using Clausius-Clapeyron equation, and discussed the meaning and the value of stress of this equation.
