Give an example of a case in which two molecules have different molecular formulas but the same empirical formula.

Explanation:

A formula which represents proportions between the elements present in a compound is known as empirical formula.

Whereas a molecular formula is defined as the formula that represents total number of each element present in a compound.

When a molecular formula is able to be reduced to smaller whole-number ratio of the elements then both molecular and empirical formulas are considered to be the same.

Relation between molecular formula and empirical formula is as follows.

               Molecular formula = n × Empirical formula

where, n is an integer.

For example, molecular formula of acetic acid is and molecular formula of formaldehyde is .

So, it means molecular formula of acetic acid can also be written as .

Therefore, we can conclude that both acetic acid and formaldehyde are two molecules that have different molecular formulas but the same empirical formula.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.