60 . E
An endothermic reaction would have ∆H° reaction >0. The relevant balanced equation is:2 C 8 H 18 + 25 O 2 → 16 CO 2 + 18 H 2 O
Since ∆H° <0and ∆S° >0, the value of ∆G° must always be negative, so the reaction is indeed
spontaneous at all temperatures (including at room temperature). Combustion (burning in air)
of organic compounds gives CO 2 and H 2 O as products, and combustion is a redox process,
since the oxidation numbers of elements are changing.61 . B
The free energy (∆G°), cell potential, and equilibrium constant of a reaction are all interrelated
and can be calculated from each other (∆G° = –RTlnK, ∆G° = –nFE°cell ). Activation energy is
independent of ∆G.
62 . C
In a saturated solution of Ca(OH) 2 at equilibrium
63 . A
An increase in temperature favors an endothermic process (in this case, the forward reaction,
because ∆H° is positive). The reaction will shift to the right, producing more moles of CO and
H 2 and consuming CH 3 OH, and the value of K will increase. Remember that a change in
temperature is the only thing that can change K.64 . A
The moles of water removed during the heating are calculated by obtaining the mass of water
removed and then converting it to moles. The mass of water evaporated off during heating of
the sample is calculated by subtracting the mass of crucible, cover and sample prior to