AnswersFL-2003350-Chemistry 1 HonorsPercent Composition and Molecular Formula

Percent Composition and Molecular Formula Answers

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1
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A sample of a compound contains 32.0 g C and 8.0 g H. Its molar mass is 30.0 g/mol. What is the compound’s molecular formula?

A
CH3
B
CH4
C
C2H4
D
C2H6
2
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Which information must be known about a compound to find the molecular formula from the empirical formula?

A
density
B
formula mass
C
percent composition
D
mole ratio
3

Webb has calculated the percent composition of a compound. How can he check his result?

A
by making sure they are in the lowest ratio
B
by adding them to see if they total 100
C
by checking that they are whole-number multiples
D
by dividing them by the molar mass
4

What is the empirical formula for a compound if a sample contains 3.72 g of P and 21.28 g of Cl?

A
PCl5
B
PCl3
C
P2Cl10
D
P2Cl5
5

What is the simplest whole-number ratio of atoms in a molecule or formula unit called?

A
the molecular formula
B
the molar mass
C
the percent composition
D
the empirical formula
6

What is the empirical formula for a compound if a sample contains 1.0 g of S and 1.5 g of O?

A
SO
B
SO3
C
S2O2
D
S2O3
7

Which step would help a student find the molecular formula of a compound from the empirical formula?

A
Multiply the subscripts of the empirical formula by the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound.
B
Subtract the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound from the subscripts of the empirical formula.
C
Divide the subscripts of the empirical formula by the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound.
D
Add the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound to the subscripts of the empirical formula.
8

What is the percent by mass of chlorine in NaCl?Use .

Question illustration
A
35.45%
B
39.34%
C
60.66%
D
70.90%
9

What is the percent by mass of sodium in ?Use

Question illustration
A
16.18%
B
22.58%
C
32.37%
D
45.98%
10

A sample of a compound contains 60.0 g C and 5.05 g H. Its molar mass is 78.12 g/mol. What is the compound’s molecular formula?

A
CH
B
C2H2
C
C6H6
D
C6H

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