Percentage Composition, Empirical and Molecular Formulae NEET Questions

Physical Chemistry - Some Basic Concepts of Chemistry

Percentage Composition, Empirical and Molecular Formulae MCQ Questions


13.
If a compound contains 70% iron and 30% oxygen by mass, the percentage of iron is closest to which oxide composition?
A.
Fe₃O₄ (magnetite)
B.
Fe₂O₃ (iron(III) oxide)
C.
FeO₂
D.
FeO (iron(II) oxide)
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ANSWER :
B. Fe₂O₃ (iron(III) oxide)
14.
In CuSO₄·5H₂O (blue vitriol), the mass percent of water of crystallization is: (CuSO₄ = 160, H₂O = 18)
A.
18%
B.
36%
C.
10%
D.
30%
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ANSWER :
B. 36%
15.
Calculate the percentage of water in washing soda (Na₂CO₃·10H₂O): (Na₂CO₃ = 106, H₂O = 18)
A.
63%
B.
20%
C.
40%
D.
80%
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ANSWER :
A. 63%
16.
In ethanol (C₂H₅OH), the mass percentages of C, H, and O respectively are:
A.
26.1%, 6.5%, 67.4%
B.
52.2%, 13.0%, 34.8%
C.
33.3%, 33.3%, 33.3%
D.
60.0%, 13.3%, 26.7%
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ANSWER :
B. 52.2%, 13.0%, 34.8%
17.
In acetic acid (CH₃COOH or C₂H₄O₂), the mass percent of C is approximately:
A.
20%
B.
40%
C.
80%
D.
60%
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ANSWER :
B. 40%
18.
In benzene (C₆H₆), the mass percent of carbon is:
A.
75.0%
B.
60.0%
C.
85.7%
D.
92.3%
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ANSWER :
D. 92.3%