3 α and 2 β emissions will be ( + + + + ). This describes what is lost from
the parent, to result in . 108 + 12 = 120 and 26 + 4 = 30. This describes .51 . A
The empirical formula of a compound is the formula that shows the smallest whole-number
relationship between the elements of a molecule. The empirical formula for this compound,
C 3 H 6 O 2 , tells us that for every 3 carbon atoms in the molecule there are 6 hydrogen atoms and
2 oxygen atoms. This does not mean that a molecule actually contains 3 carbons, 6 hydrogens,
and 2 oxygens (though it might); instead, it tells us the ratio among them. Therefore, the
molecular formula could be choice C, C 9 H 18 O 6 , where the carbon, hydrogen, and oxygen ratio
is 3:6:2 as in the empirical formula, but might also be choice A, where the ratio is correct.
Knowing that the mass of the molecule is 148 amu can help you distinguish between choices A
and C. Amu stands for atomic mass units, and means that the compound has a molecular
weight of 148 grams/mole. Choice A has an MW = 148 grams/mole while choice C has an MW =
222 grams/mole.
52 . C
The equilibrium constant expression shows the product of the product concentrations raised
to their stoichiometric coefficients over the product of the reactant concentrations raised to
their stoichiometric coefficients. For heterogeneous equilibria, pure solids and liquids are not
included in this equation; gases and aqueous components are included. You need to construct
the correct equilibrium constant expression and calculate the equilibrium constant: [H 2 ]
[I 2 ]/[HI]^2.
53 . A
The addition of a catalyst lowers the activation energy for a reaction.
54 . C
Le Châtelier’s principle says that a system will try to relieve stress put on it. An increase in
pressure will drive the reaction to the side of an equation with fewer moles of gas. Since both
sides have 2 moles of gas, an increase in pressure would not shift the equilibrium.
55 . D