Post Utme Chemistry Past Questions and Answers

Question 176:

In the redox reaction \(2 \mathrm{Fe}^{2+}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{Fe}^{3+}+2 \mathrm{Cl}^{-}\)

A. \(\mathrm{Cl}_{2}\) is reduced because it has lost electrons
B. \(\mathrm{Cl}_{2}\) is reduced because its oxidation number has decreased
C. \(\mathrm{Fe}^{2+}\) is reduced because it has lost electrons
D. \(\mathrm{Fe}^{2+}\) is reduced because it has gained electrons

Question 177:

During electrolysis of molten sodium chloride;

A. Chlorine atom gains an electron
B. Chloride ion gains an electron
C. Chloride ion is oxidized
D. Sodium ion is oxidized

Question 178:

Coffee stains are removed with ____________

A. Turpentine
B. Ammonia
C. Borax in water
D. Kerosene

Question 179:

What is the value of All for this reaction?
\(\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+3 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{Fe}(\mathrm{OH})_{3}(\mathrm{~s})\)
\begin{tabular}{|l|l|}
\hline Substance & \(\Delta \mathrm{Hf}(\mathrm{KJ} / \mathrm{mol})\) \\
\hline \(\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})\) & \(-824.2\) \\
\hline \(\mathrm{Fe}(\mathrm{OH})_{3}(\mathrm{~s})\) & \(-823.0\) \\
\hline \(\mathrm{H}_{2} \mathrm{O}(\mathrm{l})\) & \(-285.8\) \\
\hline
\end{tabular}

A. \(35.6 \mathrm{KJ}\)
B. \(286.0 \mathrm{KJ}\)
C. \(858.6 \mathrm{KJ}\)
D. \(-536 \mathrm{KJ}\)

Question 180:

\(\mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{~g})=2 \mathrm{NO}_{2}(\mathrm{~g}) \Delta \mathrm{H}=+\mathrm{ve}\) What happens to the equilibrium constant of the reaction above if the pressure is increased?

A. It becomes zero
B. It decreases
C. It increases
D. It is unaffected