ECAT Chemistry MCQs

Percent yield is actual divided by theoretical times 100.
8/10×100 = 80%.

Molality is based on solvent mass.
It is largely independent of temperature.

Molarity equals moles divided by liters of solution.
0.50/2.0 = 0.25 M.

Mass percent expresses composition on a mass basis.
All component mass percentages sum to 100%.

Mole ratios convert amounts of one substance into another.
They come directly from the balanced equation.

Chemical reactions rearrange atoms but do not create or destroy them.
Therefore total mass remains constant in a closed system.

A pure compound has constant composition.
This is also called the law of constant composition.

Percent composition is calculated from formula mass contributions.
The element percentages sum to approximately 100%.

Stoichiometry uses balanced equations to relate amounts.
It supports mass, mole, particle, and gas calculations.

Moles equal mass divided by molar mass.
18 g ÷ 18 g/mol = 1 mol.

Balancing follows conservation of atoms and mass.
Coefficients change amounts, not chemical formulas.

Chemistry examines what matter is made of and how it behaves.
It also studies energy changes accompanying chemical processes.