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WorksheetsEmpirical and Molecular Formula
Total questions: 20
Worksheet time: 10mins
Chemists use different formulas to describe compounds. The formula that shows the simplest whole-number ratio of atoms is called the:
Empirical formula
Expanded formula
Molecular formula
Structural formula
A student sees the chemical formula H₂O, which shows the actual number of atoms present in water. What kind of formula is this?
Chemical symbol
Empirical formula
Isotope notation
Molecular formula
Subscripts in a chemical formula are very important. What do they tell us?
The molar mass of the compound
The state of matter of the compound
The number of bonds between atoms
The number of atoms of each element
Vinegar is used in cooking and cleaning. Its molecular formula is C₂H₄O₂. What is its empirical formula?
CHO
CH₂O
C₂H₄O₂
C₄H₈O₄
Bleach is used as a disinfectant. If its chemical formula is Nalo, what does the subscript in ClO mean?
The total molar mass
The number of bonds
The number of isotopes
The number of atoms of each element
Salt (NaCl) is widely used for cooking. What is the relation between its empirical and molecular formula?
They are the same
They are always different
Salt has no molecular formula
The empirical formula does not apply to ionic compounds
A sample contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen. What is the empirical formula?
CH₂O
C₂H₄O₂
C₆H₁₂O₆
C₂H₂O
Sometimes, the molecular formula is a multiple of the empirical formula. Why does this happen?
Because atoms cannot combine in fractions
Because molecular formulas ignore atom ratios
Because empirical formulas always reduce to single atoms
Because molecules may contain more atoms than the simplest ratio
Learners are asked to compare empirical and molecular formulas. Which statement is correct?
Empirical formulas give more structural information
Empirical formulas always equal molecular formulas
Molecular formulas only show ratios, not actual counts
Molecular formulas can be a multiple of empirical formulas
Methane gas is used for cooking in many households. Its molecular formula is CH₄. What is its empirical formula?
CH₂
CH₄
C₂H₂
C₃H₆
A compound has an empirical formula of CH. Which molecular formula could belong to it?
CH₄
C₂H₂
C₄H₆
C₆H₆
The molecular formula of ethylene is C₂H₄. What is its empirical formula?
CH₂
C₂H₄
C₄H₈
C₆H₆
A snack contains a compound with 80% carbon and 20% hydrogen by mass. What is the empirical formula of the compound?
CH
C₂H
CH₂
C₃H
Vitamin C has an empirical formula of C₃H₄O₃. Its molar mass is 176 g/mol, while the molar mass of the empirical formula is 88 g/mol. What is its molecular formula?
C₂H₂O₂
C₃H₄O₃
C₆H₈O₆
C₉H₁₂O₉
A gas used in industry has an empirical formula of NO₂. Its molar mass is 92 g/mol, while the empirical formula mass is 46 g/mol. What is its molecular formula?
NO₂
N₂O₂
N₂O₄
N₄O₈
Plastic products may contain compounds with the empirical formula CH₂. Which of the following is NOT a possible molecular formula for such compounds?
C₂H₄
C₃H₆
C₄H₈
C₅H₁₀
Two fuel samples both have the empirical formula CH₂ but different molecular formulas. What does this show?
They are acids
They are isomers
They are isotopes
They are mixtures
A student writes the empirical formula of benzene (C₆H₆) as C₆H₆. What mistake did the student make?
They forgot to double it
They needed to add oxygen
They should have written C₃H₃
They should have reduced it to CH
A classmate insists that the empirical formula of vinegar is C₂H₄O₂, but you say it is CH₂O. Who is correct?
Both, because they mean the same thing
Neither, because vinegar has no formula
Your classmate, because vinegar has two carbons
You, because the ratio 2:4:2 can be simplified to 1:2:1
A chemist tests a fuel with an empirical formula of CH and a molar mass of 78 g/mol. The molar mass of CH is 13 g/mol. Should the chemist conclude that the molecular formula is C₆H₆?
Yes, because 13 × 6 = 78
No, because CH cannot exist
Yes, because all fuels have the same formula
No, because the molecular formula must be CH₂
