Answers FL-2003350-Chemistry 1 HonorsPercent Composition and Molecular Formula

Percent Composition and Molecular Formula Answers

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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?

empirical formula mass / molecular mass = n

molecular mass = element mass / empirical formula mass ´ 100

subscript of H in empirical formula = 2 subscript of H in molecular formula

subscript of C in molecular formula = n subscript of C in empirical formula

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

by making sure they are in the lowest ratio

by adding them to see if they total 100

by checking that they are whole-number multiples

by dividing them by the molar mass

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

They are always different for the same compound.

Subscripts of empirical formulas can be reduced.

Molecular formulas can be determined from empirical formulas.

They both show the actual ratio of elements for a compound.

What is the empirical formula for C2H6?

CH3

C2H4

C6H18

Which information must be known about a compound to find the molecular formula from the empirical formula?

density

formula mass

percent composition

mole ratio

Which represents the empirical formula for A3B9?

AB3

AB2

A3B9

A9B27

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

PCl5

PCl3

P2Cl10

P2Cl5

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

the molecular formula

the molar mass

the percent composition

the empirical formula

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

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.

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.

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.

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.

The percent by mass of copper in CuBr2 isUse .

28.45%.

44.30%.

63.55%.

71.55%.

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Percent Composition and Molecular Formula Answers

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