Pakistan MCQs

The system consumes some added reactant.
The shift reduces the imposed concentration change.

Standard formation enthalpies are tabulated reference values.
Elements in their standard states have ΔHf° defined as zero.

The reaction produces more product to replace what was removed.
This is an application of Le Chatelier's principle.

Bond enthalpies are average values for many molecules.
Breaking bonds requires energy, while forming bonds releases energy.

Higher pressure favors the side occupying less gas volume.
That is usually the side with fewer gas moles.

Energy may be transferred as heat or work.
It is not created or destroyed.

A catalyst lowers activation energies for both directions.
It speeds equilibration without changing the equilibrium position.

Greater dispersal and more possible arrangements generally mean higher entropy.
Gases usually have higher entropy than liquids or solids.

Temperature alters the balance between forward and reverse energetics.
K is constant only at a specified temperature.

Spontaneity describes direction, not speed.
A spontaneous reaction may still be very slow.

Gibbs energy change is ΔG=ΔH-TΔS.
Negative ΔG indicates a thermodynamically favorable direction.

At equilibrium there is no net driving force for change.
The reaction mixture has minimum Gibbs energy under the conditions.