If the pressure and temperature of a gas are held constant, the final volume of a gas will increase only if the number of moles of gas decreases. true false

This is false.  If pressure and temperature are held constant and you decrease the number of moles, the volume of the gas should decrease as well.

The most plausible answer is b, duration. the given amount of time is considered how long it last for.

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.