27 . A
Hydrogen peroxide has the empirical formula HO.28 . E
No reaction takes place. In order for a reaction to take place to produce H 2 O, energy must be
added to the system (typically in the form of heat).
29 . A
Choice A, which says that an electron may assume an infinite number of different velocities, is
true in classical mechanics but not in Bohr’s model. Bohr used quantum theory in developing
his atomic model and placed specific conditions on the possible values of the electron
velocity. Since we’re looking for the incorrect statement, choice A is the correct answer.
30 . A
100 g O 2 divided by 32 g/mol = 3.125 moles of oxygen. You’re given 296 kJ/mol in the equation
(a negative value means heat is released), so multiply 296 kJ/mole × 3.125 mole to get 925 kJ.
925 kJ is equal to 925,000 joules of heat.
31 . E
At 10 cents/coulomb, the question is really asking you which reaction involves the transfer of
the most electrons.
Cu from Cu2+ 2 electrons
Na from Na+ 1 electron
Cl from Cl− 1 electron
H from H+ 1 electron
Fe from Fe3+ 3 electronsTherefore, the production of Fe from Fe3+ involves the transfer of the most electrons and
would cost the most.32 . D