Interpretation:
The molecular formula of caffeine needs to be determined when the percent composition of caffeine is 49.5% C, 5.20% H, 16.5% O, and 28.9% N and its molar mass is 194.1 g/mol.
Concept Introduction:
The ratio of number of atoms is equal to fractions ratio of their percentage and relative
Answer to Problem 77A
The molecular formula of caffeine is
Explanation of Solution
Step 1:
From the periodic table in the textbook, it is known as:
Step 2:
The ratio of number of atoms is equal to fractions ratio of their percentage and relative atomic mass so one has as:
Step 3:
The numbers are divided with smallest one.
Thus, the empirical formula is
Step 4:
The molar mass is as:
Step 5:
Empirical formula is simplest ratio of number of atoms in molecule and a molecular formula is whole number product of an empirical formula.
Molecular formula of caffeine is
Hence the molecular formula is
Chapter 11 Solutions
Chemistry 2012 Student Edition (hard Cover) Grade 11
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