Oxidation–Reduction Reactions
Consider the following equation:
$$6 \mathrm{Na}(s)+2 \mathrm{NH}_{3}(a q) \rightarrow 2 \mathrm{Na}_{3} \mathrm{N}(s)+3 \mathrm{H}_{2}(g)$$
Which species acts as an oxidizing agent?
(A) $\mathrm{Na}$
(B) $\quad \mathrm{N}$ in $\mathrm{NH}_{3}$
(C) $\quad \mathrm{H}$ in $\mathrm{NH}_{3}$
(D) $\quad \mathrm{H}_{2}$
How many electrons are involved in the following half-reaction after it is balanced?
$$\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{H}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Cr}^{2+}+\mathrm{H}_{2} \mathrm{O}$$
$(A)$
$(C)$
Lithium aluminum hydride (LiAlH_) is often used in laboratories
because of its tendency to donate a hydride ion. Which of the
following roles would lithium aluminum hydride likely play in a
(A) $\quad$ Strong reducing agent only
(B) $\quad$ Strong oxidizing agent only
(C) $\quad$ Both a strong reducing agent and strong oxidizing agent
(D) $\quad$ Neither a strong reducing agent nor a strong oxidizing
What is the oxidation number of chlorine in $\mathrm{NaClO}$ ?
(D) +2
The following electronic configurations represent elements in their neutral form. Which element is the strongest oxidizing agent?
$1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2}$
(B) $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{5}$
$1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{10} 4 p^{1}$
$(\mathrm{D})$
Which of the following is the correct net ionic reaction for the reaction of copper with silver(l) nitrate?
(A) $\quad \mathrm{Cu}+\mathrm{AgNO}_{3} \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{Ag}$
(B) $\mathrm{Cu}+2 \mathrm{Ag}^{+}+2 \mathrm{NO}_{3}^{-} \rightarrow \mathrm{Cu}^{2+}+2 \mathrm{NO}_{3}^{-}+2 \mathrm{Ag}$
(C) $2 \mathrm{Ag}^{+}+2 \mathrm{NO}_{3}^{-} \rightarrow 2 \mathrm{NO}_{3}^{-}+2 \mathrm{Ag}^{+}$
(D) $\quad \mathrm{Cu}+2 \mathrm{Ag}^{+} \rightarrow \mathrm{Cu}^{2+}+2 \mathrm{Ag}$
One way to test for the presence of iron in solution is by adding potassium thiocyanate to the solution. The product when this reagent reacts with iron is $\mathrm{FeSCN}^{2+}$, which creates a dark red color
in solution via the following net ionic equation:
$$\mathrm{Fe}^{3+}+\mathrm{SCN}^{-} \rightarrow \mathrm{FeSCN}^{2+}$$
How many grams of iron sulfate would be needed to produce 2 moles of $\mathrm{FeSCN}^{2+}$ ?
$$\begin{array}{ll}
\text { (A) } & 110 \mathrm{g} \\
\text { (B) } & 220 \mathrm{g} \\
\text { (C) } & 400 \mathrm{g} \\
\text { (D) } & 500 \mathrm{g}
\end{array}$$
During the assigning of oxidation numbers, which of the following
elements would most likely be determined last?
(A) $\quad \mathrm{Ar}$
(B) $F$
$(\mathrm{C})$
As methanol is converted to methanal, and then methanoic acid,
the oxidation number of the carbon:
(A) increases.
(B) decreases.
(C) $\quad$ increases, then decreases.
(D) decreases, then increases.
In the compound $\mathrm{KH}_{2} \mathrm{PO}_{4}$, which element has the highest oxidation
number?
(A) $k$
(B) $H$
(C) $\quad P$
(D) O
If a certain metal has multiple oxidation states, its acidity as an oxide generally increases as the oxidation state increases.
Therefore, which of the following tungsten compounds is likely to
be the strongest acid?
\text { (A) } & \mathrm{WO}_{2} \\
\text { (B) } & \mathrm{WO}_{3} \\
\text { (C) } & \mathrm{W}_{2} \mathrm{O}_{3} \\
\text { (D) } & \mathrm{W}_{2} \mathrm{O}_{5}
Consider the following steps in the reaction between oxalic acid
and chlorine:
$$\begin{array}{l}
\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{HOCl}+\mathrm{Cl}^{-}+\mathrm{H}^{+} \\
\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \rightarrow \mathrm{H}^{+}+\mathrm{HC}_{2} \mathrm{O}_{4}^{-} \\
\mathrm{HOCl}+\mathrm{HC}_{2} \mathrm{O}_{4}^{-} \rightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{Cl}^{-}+2 \mathrm{CO}_{2}
Which of these steps, occurring in aqueous solution, is an example
of a disproportionation reaction?
(A) $\quad$ I only
(B) $\quad \|$ only
(C) $\quad$ I and III only
(D) $\quad \mid, \|,$ and \|\|
Potentiometry in an oxidation-reduction titration is analogous to
performing an acid-base titration with a(n):
acidic indicator.
(B) basic indicator.
(C) $\quad$ pH meter.
(D) $\quad$ oxidizing agent
After balancing the following oxidation-reduction reaction, what is the sum of the stoichiometric coefficients of all of the reactants
and products?
$$\mathrm{S}_{8}(s)+\mathrm{NO}_{3}^{-}(a q) \rightarrow \mathrm{SO}_{3}^{2-}(a q)+\mathrm{NO}(g)$$
(D) 115
An assay is performed to determine the gold content in a supply of
crushed ore. One method for pulling gold out of ore is to react it in a concentrated cyanide (CN") solution. The equation is provided below:
$$\mathrm{Au}+\mathrm{NaCN}+\mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Na}\left[\mathrm{Au}(\mathrm{CN})_{2}\right]+\mathrm{NaOH}$$
An indicator is used during this reaction, and approximately 100 $\mathrm{mL}$ of a $2 \mathrm{M} \mathrm{NaCN}$ solution is used to reach the endpoint. How
many moles of Au are present in the crushed ore?
$0.01 \mathrm{mol}$
(B) $0.02 \mathrm{mol}$
(D) $0.20 \mathrm{mol}$