Question

two different ionic compounds each contain only copper and chlorine. both compounds are powders, one white and one brown. an elemental analysis is performed on each powder. which of the following questions about the compounds is most likely to be answered by the results of the analysis?
a what is the density of each pure compound?
b what is the formula unit of each compound?
c what is the chemical reactivity of each compound?
d which of the two compounds is more soluble in water?

Explanation:

• Option A: Density depends on mass and volume, which aren't determined by elemental analysis (which gives the ratio of elements). So A is incorrect.
• Option B: Elemental analysis gives the relative amounts (moles) of copper and chlorine in each compound. From this, we can find the empirical formula (formula unit) of the ionic compound (since ionic compounds are represented by formula units). This is directly answerable by elemental analysis.
• Option C: Chemical reactivity depends on factors like bond strength, oxidation states, and reaction conditions, not just elemental composition. Elemental analysis doesn't provide reactivity info. So C is incorrect.
• Option D: Solubility in water depends on lattice energy, ion - dipole interactions, etc., and isn't determined by elemental analysis (which only tells the ratio of elements). So D is incorrect.

Answer:

B. What is the formula unit of each compound?