Question

based on what you now know about the different formulas, lets see how this relates to your objective for this lesson. if you want to know the identity of an unknown substance, what type of formula would you most likely want to know? a. molecular formula b. empirical formula c. structural formula either a or c b only either a or b a, b and c

Explanation:

• Molecular formula: Gives the exact number of atoms of each element in a molecule. For example, \(H_2O_2\) (hydrogen peroxide) tells us there are 2 hydrogen and 2 oxygen atoms.
• Empirical formula: Gives the simplest whole - number ratio of atoms of each element in a compound. \(HO\) is the empirical formula for hydrogen peroxide (simplest ratio of \(H:O = 1:1\)). But it doesn't uniquely identify a substance as multiple substances can have the same empirical formula. For example, \(C_2H_4\) (ethylene) and \(C_3H_6\) (propylene) have the same empirical formula \(CH_2\).
• Structural formula: Shows how the atoms are arranged in a molecule. The structural formula of \(H - O - O - H\) for hydrogen peroxide gives information about the bonding between atoms. Different structural arrangements can lead to different chemical and physical properties. For example, isomers (like butane and isobutane) have the same molecular formula (\(C_4H_{10}\)) but different structural formulas and different properties.

To know the identity of an unknown substance, both the molecular formula (gives the elemental composition in terms of exact atom numbers) and the structural formula (gives the arrangement of atoms which is crucial for properties) are important. The empirical formula alone is not sufficient as it is too simplistic and non - unique.

Answer:

Either A or C