Question

Three elements, A, Q, and Z, have the molar masses indicated in the table below. Given a compound with a composition of 15.66% A and 84.34% Z by mass, what is the empirical formula of this compound?
element symbol molar mass
A 15.45 g/mol
Q 20.05 g/mol
Z 41.62 g/mol

Answer 1

Answer:

AZ₂

Explanation:

The formed compound will not contain Q because mass percentages, %A and %B, form 100% of the compound.

Steps

1. Change % of each element into grams.
2. Convert grams of each element into moles by dividing grams by molar mass.
3. Divide all moles by the smallest number of moles.
4. If the moles are all whole numbers, then you’re done and that’s your empirical formula.
5. If not, multiply all moles by number such that everything is a whole number.

Solving

• We have 15.66g of A and 84.34g of Z
• Moles of A, n(A) = 15.66/15.45 = 1.01 moles
• Moles of Z, n(Z) = 84.34/41.62 = 2.02 moles
• A = 1.01/1.01 = 1 and Z = 2.02/1.01 = 2
• Therefore, the empirical formula is AZ₂