Concept explainers
Lysine, an essential amino acid in the human body, contains

Interpretation:
The empirical and molecular formula of lysine is to be determined with given mass of lysine, mass of carbon dioxide, and mass of water.
Concept introduction:
Empirical formula is the simplest formula of any compound when written in the least possible whole number without altering the relative number of atoms.
The molecular mass of any compound is the sum of the atomic masses of every element that is present in the molecule of the compound. It is denoted by M. The unit of molecular mass isamu.
When any hydrocarbon has completely reacted with oxygen, then the product formed contains
The percent composition of an element by its mass in a compound can be calculated as
Here, n represents the number of atoms in the given molecule or compound.
The number of moles is defined as the ratio of mass to the molar mass:
Here,
The mass of compound can be calculated as
Here,
The molecular formula can be calculated as
Answer to Problem 149AP
Solution:
(a)
(b)
Explanation of Solution
a) The empirical formula of lysine
The molar mass of carbon dioxide is
Calculate the mass of carbon dioxide as
Substitute
The molar mass of hydrogen is
Calculate the mass of water as
Substitute
The molar mass of nitrogen is
Calculate the mass of ammonia as
Substitute
Calculate the mass percent of carbon as
Calculate the mass percent of hydrogen as
Calculate the mass percent of nitrogen as
Calculate the mass percent of oxygen as
Now, calculate the number of moles by assuming the sample to be 100 g.
The molar mass of carbon is
Calculate the number of moles of carbon as
Substitute
The molar mass of hydrogen is
Calculate the number of moles of hydrogen as
Substitute
The molar mass of nitrogen is
Calculate the number of moles of nitrogen as
Substitute
The molar mass of oxygen is
Calculate the number of moles of oxygen as
Substitute
Calculate the ratio of carbon, hydrogen, nitrogen, and oxygen as
Hence, the empirical formula of lysine is
b)The molecular formula of the compound
The molecular mass of lysine is 150 g.
Calculate the empirical formula mass of lysine as
Now, the whole number multiple
Substitute
Calculate the molecular formula as
Substitute 2 for
Hence, themolecular formula of lysine is
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Chapter 3 Solutions
BURDGE CHEMISTRY VALUE ED (LL)
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