NAT Chemistry MCQs

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.

Equation coefficients give stoichiometric ratios.
They may be interpreted as molecule or mole ratios.

Once the limiting reactant is used up, no more product can form.
Other reactants may remain in excess.

An element cannot be broken down chemically into simpler substances.
Each element is identified by its atomic number.

An excess reactant is supplied beyond the stoichiometric requirement.
Some remains when the reaction is complete.

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.