- C Deoxyribose is a ribose sugar molecule missing an oxygen atom. As
with all molecules with the suffix -ose, ribose is a carbohydrate. In
general, proteins tend to have the suffix -in (or -ase if they are an
enzyme) and nucleic acids have the suffix -ine (except for uracil). - E Electrolytes are substances that increase the electrical conductivity of
water by dissolving in solution to form ions. Therefore, all ionic
compounds, or salts, are electrolytes. - D Most lipids are insoluble in water. For example, fat-based oils (such as
corn oil), a subfamily of lipids, form droplets in water. Several other fat
derivatives form double-layered sheets in water; this type of lipids serves
as the principle structural element in cell membranes. - E Don’t let phrases such as “constituent elements” throw you off course.
The question asks you to identify a situation in which a compound is
broken down into its elements. Mercury(II) oxide, HgO, is decomposed
into the elements mercury, Hg, and oxygen, O 2 , in choice (E). - C When a radioactive atom undergoes alpha decay, it loses 2 protons and 2
neutrons. That means that its atomic number decreases by 2, and its mass
number decreases by 4. That’s exactly what has happened here. Uranium
(atomic number = 92, mass number = 234) has been converted to thorium
(atomic number = 90, mass number = 230). - E The phrase “oxidation-reduction reaction” describes a reaction in which
one atom loses electron(s) to another. The atom that loses electrons is
oxidized, and the one that gains electrons is reduced. In HgO, the
oxidation state of Hg is +2 and that of oxygen is −2. HgO is decomposed
into the free elements Hg and O 2 , each of which has an oxidation state of
0. So the oxidation state of Hg goes from +2 to 0; it has been reduced.
Oxygen has been oxidized; its oxidation state has changed from −2 to 0.
This is clearly a redox reaction. - B Look at choice (B). In an atom of carbon-14 there are 8 neutrons and 6
protons, a ratio greater than 1. In nitrogen-14, the neutron-to-proton ratio
is 7:7 or equivalent to 1. Choice (B) is an example of beta decay. As you
can see, beta decay causes the neutron-to-proton ratio to decrease.
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