ECAT MCQs

Compounds have definite formulas and characteristic properties.
Their components can be separated only by chemical means.

Theoretical yield assumes complete reaction and no losses.
It is calculated from the limiting reactant.

Mixture components retain much of their individual identity.
They can often be separated by physical methods.

Actual yield is measured after the experiment.
It is usually lower than theoretical yield.

Solutions are homogeneous mixtures.
Any sampled portion has approximately the same composition.

Percent yield measures reaction and recovery efficiency.
Values below 100% commonly result from losses or incomplete reaction.

Heterogeneous mixtures contain distinguishable regions or phases.
Examples include sand in water and granite.

A physical change alters form or state without changing chemical identity.
Ice and liquid water are both H2O.

Rusting forms new iron oxide substances.
Chemical changes involve rearrangement of atoms and new products.

Density describes how much mass is packed into a volume.
It is commonly expressed in g/cm³ or kg/m³.

The mole is the SI base unit for amount of substance.
One mole contains Avogadro's number of specified entities.

Avogadro's constant gives the number of entities in one mole.
The entities may be atoms, molecules, ions, or formula units.