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An empirical formula is the simplest whole-number ratio of a molecular formula. The EF may or may not be the same as the MF. Data used to determine the EF may be the masses of or percentages elements that comprise the compound. If the percentages are given, you may assume that there is 100 grams of the compound provided, and the percentages are equal to the masses of the elements. Convert these into moles by dividing by the molar mass, and then divide that number by the smallest value to get the ratio. To get the molecular formula, you must divide the molar mass of the empirical formula into the given molecular formula mass to find the multiplier. Then multiply that number by the EF to get the MF. To complete this quiz, you must have a periodic table and a calculator. This quiz covers simple empirical and molecular formula calculations.
You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements.
S2O
SO3
SO
SO2
What is the empirical formula if you have 81.82% carbon and 18.18% hydrogen?
CH5
C3H8
C2H5
CH
Given the following: 42.07% Na, 18.89% P, and 39.04% O, determine the empirical formula.
Na3PO5
NaPO4
Na3PO4
Na3PO2
What is the empirical formula if you have 35.98% aluminum and 64.02% sulfur?
AlS
Al2S3
Al2S
Al4S3
What is the empirical formula if you have 36.84% nitrogen and 63.16% oxygen?
N2O
NO3
NO
N203
A gas sample is found to contain 39.10% carbon, 7.67% hydrogen, 26.11% oxygen, 16.82% phosphorus, and 10.30% fluorine. If the molecular mass is 184.1 g/mol, what is the molecular formula?
C6HO3PF
C6H14O3PF
C6H14OF
C6H14O3PF3
A compound contains 46.7% nitrogen and 53.3% oxygen. If the molecular mass of the compound is 60.0 g/mol, what is the molecular formula?
NO
N2O2
N2O
NO2
A compound is found to contain 24.8% carbon, 2.0% hydrogen, and 73.2% chlorine with a molecular mass of 96.9 g/mol. What is the molecular formula?
CH2Cl2
C2H2Cl
C2H2Cl2
C2HCl
