ECAT Chemistry MCQs

Calorimeters track temperature changes in known heat capacities.
They help determine reaction or phase-change energy.

Enthalpy is a state function.
Therefore the path between initial and final states does not affect ΔH.

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

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

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

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

Crystalline solids have repeating lattice structures.
They often have sharp melting points.

The system may be a reaction mixture, gas, or other selected matter.
Everything else is called the surroundings.

Glass is a common amorphous solid.
Such solids often soften over a temperature range.

The surroundings can exchange energy or matter with the system depending on the boundary.
System plus surroundings form the universe.

The solvent is usually the component in larger amount.
The solute is dispersed at the molecular or ionic level.

Open systems allow material flow across their boundaries.
Many industrial reactors are open systems.