SAT Subject Test Chemistry,10 edition

(Marvins-Underground-K-12) #1
outlined,   the amount  of  heat    needed  to  perform each    of  them    must    be  calculated  using   the
following equation:

5 . B


This    problem uses    Hess’s  law,    which   states  that    heats   of  reaction    may be  added   to  determine
the enthalpy of another reaction. To calculate the heat of formation for one mole of carbon
monoxide, the reaction equations must be manipulated as follows:

The second  equation    must    be  reversed:

If  the two equations   are added   together,   a   third   equation    is  obtained:

This    is  the formation   reaction    of  carbon  monoxide.   As  in  question    3,  however,    we  need    to
divide the enthalpy change by two to obtain the value for 1 mole.

6 . D
A negative free energy change signifies that the reaction is spontaneous and that work can be
done. If the energy that is released is coupled to less favorable reactions, they can be driven to
completion. This, for example, is how your body uses the breakdown of ATP to accomplish
certain reactions that normally wouldn’t occur.


7 . B

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