Smoke volatility index is equal to smoke point plus________?

Pick out the wrong statement?

A typical example of an exothermic reversible reaction conducted at high pressure in industry is________?

The function of skimming tank in sewage treatment is to remove ________ substances?

Vent pipes are provided in a condenser to ________?

Efficiency of a Carnot engine working between temperatures T1 and T2 (T1 < T) is ________?