Post Utme Chemistry Past Questions and Answers

Question 81:

\(15 \mathrm{~g}\) of impure \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) reacted with excess \(\mathrm{HNO}_{3}\). If \(0.1\) mole of \(\mathrm{CO}\), is produced, what is the percentage purity of the \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) ? \([\mathrm{Na}=23, \mathrm{C}=12,0=16]\)

A. \(35.3 \%\)
B. \(10.0 \%\)
C. \(70.66 \%\)
D. \(90.0 \%\)

Question 82:

\(0.14 \mathrm{~g}\) of a hydride of carbon occupies \(112.0 \mathrm{~cm}^{3}\) at STP when evaporated. The ratio of carbon to hydrogen is \(1: 2\). The relative molecular formula is ____________

A. \(\mathrm{C}_{2} \mathrm{H}_{4}\)
B. \(\mathrm{C}_{3} \mathrm{H}_{6}\)
C. \(\mathrm{C}_{4} \mathrm{H}_{8}\)
D. \(\mathrm{C}_{6} \mathrm{H}_{12}\)

Question 83:

A gas \(X\) diffuses twice as fast as a gas \(Y\) under the same conditions. If the relative molecular mass of \(\mathrm{Y}\) is 112 , calculate the relative molecular mass of \(X\).

A. 28
B. 14
C. 56
D. 120

Question 84:

In the periodic table, what is the property that decreases along the period and increases down the group?

A. Atomic number
B. Electron affinity
C. Ionization potential
D. Ionic radius

Question 85:

\(10 \mathrm{~cm}^{3}\) of \(0.1 \mathrm{M} \mathrm{HCL}\) are added to \(10 \mathrm{~cm}^{3}\) of \(\mathrm{NaOH}\) solution containing \(8 \mathrm{~g}\) of \(\mathrm{NaOH}\) per \(\mathrm{dm}^{3}\) of solution. What is the \(\mathrm{pH}\) of the resulting solution? 9. The solubility of alkanols in water is due to ____________

A. 11
B. 13
C. 7
D. 8