Questions 1-35 (thirty five questions) Directions: Each of the questions or incomplete statements in this section is followed by four suggested answers. Select the best answer in each case.

Amphoteric oxides react with both acids and bases. Among the given options, tin(II) oxide ($\text{SnO}$) is known to be amphoteric. Carbon monoxide ($\text{CO}$) is neutral, and silicon dioxide ($\text{SiO}_2$) is acidic.
The correct option is B.

A primary standard is a substance used to prepare a standard solution. It must be of high purity, stable, non-hygroscopic, and have a high molar mass.

• $\text{KOH}$ is hygroscopic.
• $\text{HCl}$ is volatile.
• $\text{H}_2\text{SO}_4$ is hygroscopic.
• $\text{Na}_2\text{CO}_3$ meets the criteria for a primary standard. The correct option is D.

Warming with aqueous sodium hydroxide suggests a hydrolysis reaction. Haloalkanes undergo nucleophilic substitution with hydroxide ions to produce alcohols.

• $\text{CH}_3\text{COOH}$ (ethanoic acid) reacts with $\text{NaOH}$ to form a salt and water.
• $\text{C}_2\text{H}_5\text{OH}$ (ethanol) is already an alcohol.
• $\text{CH}_2=\text{CH}_2$ (ethene) undergoes addition reactions, not typically hydrolysis to an alcohol with $\text{NaOH}$.
• $\text{CH}_3\text{CH}_2\text{Br}$ (bromoethane) reacts with $\text{NaOH}$ to form $\text{CH}_3\text{CH}_2\text{OH}$ (ethanol). The correct option is D.

The mole fraction of a component in a mixture is given by the moles of that component divided by the total moles of all components.
Moles of methanol = 2.0 moles
Moles of ethanol = 3.0 moles
Total moles = $2.0 + 3.0 = 5.0$ moles
Mole fraction of methanol = $\frac{\text{Moles of methanol}}{\text{Total moles}} = \frac{2.0}{5.0} = 0.40$
The correct option is B.

Propanal ($\text{CH}_3\text{CH}_2\text{CHO}$) is an aldehyde, and propanone ($\text{CH}_3\text{COCH}_3$) is a ketone. Both have the same molecular formula ($\text{C}_3\text{H}_6\text{O}$) but different functional groups. This is an example of functional group isomerism.
The correct option is D.

The relative molecular mass (RMM) of $\text{Na}_2\text{CO}_3$ is given as 106.
Moles of $\text{Na}_2\text{CO}_3 = \frac{\text{Mass}}{\text{RMM}} = \frac{21.2 \text{ g}}{106 \text{ g/mol}} = 0.2 \text{ mol}$
Since one molecule of $\text{Na}_2\text{CO}_3$ contains one carbonate ion ($\text{CO}_3^{2-}$), the number of moles of carbonate ions is equal to the number of moles of $\text{Na}_2\text{CO}_3$.
Moles of $\text{CO}_3^{2-}$ ions = $0.2 \text{ mol}$
The correct option is B.

The nuclear reaction is:

For conservation of mass number (superscript):
$235 + 1 = 141 + \text{Mass number of X} + 3 \times 1$
$236 = 141 + \text{Mass number of X} + 3$
$236 = 144 + \text{Mass number of X}$
$\text{Mass number of X} = 236 - 144 = 92$

For conservation of atomic number (subscript):
$92 + 0 = 56 + \text{Atomic number of X} + 3 \times 0$
$92 = 56 + \text{Atomic number of X}$
$\text{Atomic number of X} = 92 - 56 = 36$

The element with atomic number 36 is Krypton ($\text{Kr}$).
So, particle X is $^{92}_{36}\text{Kr}$.
The correct option is A.

A condensation reaction involves the joining of two molecules with the elimination of a small molecule, typically water.

• $\text{Ethanoic acid}$ (a carboxylic acid) and $\text{ethanol}$ (an alcohol) undergo esterification, which is a type of condensation reaction, to form an ester and water. The correct option is B.

The balanced neutralization reaction is:

From the stoichiometry, 1 mole of $\text{H}_2\text{SO}_4$ reacts with 2 moles of $\text{NaOH}$.

Given:
Concentration of $\text{NaOH}$ ($C_{\text{NaOH}}$) = 0.2 M
Volume of $\text{NaOH}$ ($V_{\text{NaOH}}$) = $20.0 \text{ cm}^3 = 0.020 \text{ dm}^3$
Concentration of $\text{H}_2\text{SO}_4$ ($C_{\text{H}_2\text{SO}_4}$) = 0.1 M

Moles of $\text{NaOH}$ = $C_{\text{NaOH}} \times V_{\text{NaOH}} = 0.2 \text{ M} \times 0.020 \text{ dm}^3 = 0.004 \text{ mol}$

From the reaction stoichiometry, moles of $\text{H}_2\text{SO}_4$ = $\frac{1}{2} \times \text{Moles of NaOH}$
Moles of $\text{H}_2\text{SO}_4 = \frac{1}{2} \times 0.004 \text{ mol} = 0.002 \text{ mol}$

Volume of $\text{H}_2\text{SO}_4$ ($V_{\text{H}_2\text{SO}_4}$) = $\frac{\text{Moles of H}_2\text{SO}_4}{C_{\text{H}_2\text{SO}_4}} = \frac{0.002 \text{ mol}}{0.1 \text{ M}} = 0.020 \text{ dm}^3$
Converting to $\text{cm}^3$: $0.020 \text{ dm}^3 \times 1000 \text{ cm}^3/\text{dm}^3 = 20.0 \text{ cm}^3$
The correct option is B.