During what change is heat absorbed?
2 answers:
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Answer:
.
Explanation:
Carbon and hydrogen are the only two elements in a hydrocarbon. When a hydrocarbon combusts completely in excess oxygen, the products would be and
. The
and
would come from the hydrocarbon, while the
atoms would come from oxygen.
Look up the relative atomic mass of these three elements on a modern periodic table:
:
.
:
.
:
.
Calculate the molar mass of and
:
.
Calculate the number of moles of molecules in
of
:
.
Similarly, calculate the number of moles of molecules in
of
:
.
Note that there is one carbon atom in every molecule. Approximately
of
molecules would correspond to the same number of
atoms. That is:
.
On the other hand, there are two hydrogen atoms in every molecule. approximately
of
molecules would correspond to twice as many
atoms. That is:
.
The ratio between the two is: .
The empirical formula of a compound gives the smallest whole-number ratio between the elements. For this hydrocarbon, the empirical formula would be .