Answers2003350 Chemistry HONORS Sem 1 - MarezPercent Composition and Molecular Formula

Percent Composition and Molecular Formula Answers

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1
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What is the percent by mass of carbon in C10 H14 N2?Use .

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A
8.71%
B
17.27%
C
69.50%
D
74.02%
2
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What is the empirical formula for C2H6?

A
CH
B
CH3
C
C2H4
D
C6H18
3

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.
4

The empirical formula for a compound is CH2. If n is a whole number, which shows a correct relationship between the molecular formula and the empirical formula?

A
empirical formula mass / molecular mass = n
B
molecular mass = element mass / empirical formula mass ´ 100
C
subscript of H in empirical formula = 2 subscript of H in molecular formula
Option C
D
subscript of C in molecular formula = n subscript of C in empirical formula
Option D
5

Which represents the empirical formula for A3B9?

A
AB3
B
AB2
C
A3B9
D
A9B27
6

Which statement best relates an empirical formula with a molecular formula?

A
They are always different for the same compound.
B
Subscripts of empirical formulas can be reduced.
C
Molecular formulas can be determined from empirical formulas.
D
They both show the actual ratio of elements for a compound.
7

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
8

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
9

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
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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