Question Library

NO\(_2\) (nitrogen dioxide) is a covalent compound, not an ionic one. It is formed by the sharing of electrons between two non-metals: nitrogen and oxygen. Unlike ionic compounds, which typically involve the transfer of electrons from a metal to a non-metal, NO\(_2\) consists solely of non-metallic elements that form molecular bonds.

Sodium carbonate (Na\(_2\)CO\(_3\)) is an alkali metal carbonate that is extremely stable and does not decompose when heated strongly, even at Bunsen burner temperatures. This stability is due to the large size and low charge density of the sodium cation (Na\(^+\)), which has low polarizing power and cannot easily distort the carbonate ion (CO\(_3\)\(^{2-}\)) to break its carbon-oxygen bonds. Most group 1 carbonates (except lithium carbonate) exhibit this high thermal stability.

A universal indicator changes colour to represent the pH level of a substance. For instance, a red colour indicates a very low pH (typically 0 to 3), which corresponds to a strong or concentrated acid; for pH 0: Specifically produces a strong red or dark red colour, representing the highest acidity and for indicator Spectrum: the colour moves from red (strong acid) to orange/yellow (weak/dilute acid), green (neutral), and finally blue/purple (bases).

Nitrogen dioxide (NO\(_2\)) is unique because it undergoes a disproportionation reaction when dissolved in water. In this reaction, the nitrogen atom (which has an oxidation state of +4 in NO\(_2\) ) is both oxidized and reduced simultaneously, resulting in the formation of two distinct acids; 2NO\(_2\) + H\(_2\)O → HNO\(_2\) + HNO\(_3\)

Ethanol (C\(_2\)H\(_5\)OH) can be prepared in the laboratory by the hydration of ethene (C\(_2\)H\(_4\)). This process involves an acid-catalyzed addition reaction where water (in the form of steam) is added across the double bond of ethene in the presence of a concentrated acid catalyst, such as phosphoric(V) acid (H\(_3\)PO\(_4\)) or sulphuric acid (H\(_2\)SO\(_4\)).

Alkali metals (Group 1 elements) have a single valence electron in their outermost shell. In a metallic lattice, these valence electrons are weakly held by the nucleus and become delocalised, meaning they are free to move throughout the entire structure.

In a chemical reaction, \DeltaH(change in enthalpy) is positive when the reaction is endothermic, meaning the system absorbs heat from its surroundings. i.e \DeltaH\(_{product}\) must be greater than \DeltaH\(_{reactant}\).

Propene (C\(_3\)H\(_6\)) is an alkene that contains one carbon-carbon double bond (C=C) and one carbon-carbon single bond (C-C). According to bonding rules: A single bond consists of exactly one sigma (σ) bond. A double bond consists of one sigma (σ) bond and one pi (\pi) bond. Because propene has only one double bond in its structure (CH\(_2\)=CH-CH\(_3\)), it contains exactly one pi bond.

Addition reactions typically occur in unsaturated hydrocarbons, which contain at least one double or triple bond between carbon atoms. As an alkene, butene contains a carbon-to-carbon double bond (C=C). This double bond can break (specifically the pi bond), allowing new atoms or groups of atoms to attach to the carbon atoms, resulting in a single saturated product. Common examples include hydrogenation (adding H\(_2\)) and halogenation (adding Cl\(_2\) or Br\(_2\))

Given: Volume, V = 200 cm\(^3\) Concentration, C = 5.6 g/dm\(^3\) Molar mass of KOH, M = 56 g/mol Number of moles, n = \(\frac{CV}{1000}\) But because mass concentration was given in g/dm\(^3\) instead of molar concentration (mol/dm\(^3\)) to enable us calculate the number of moles, we'll have to convert concentration from mass to molar using the relationship below: Molar concentration (mol/dm\(^3\)) = \(\frac{mass concentration}{Molar Mass}\) = \(\frac{5.6}{56}\) = 0.1 mol/dm\(^3\) Now, we can find the number of moles using, Number of moles, n = \(\frac{0.1 X 200}{1000}\) = 0.02 mole The correct answer is option C

Water is the only covalent hydride in the list that is a liquid at room temperature due to intermolecular hydrogen bonding. Oxygen is highly electronegative and small in size, allowing it to form strong hydrogen bonds between molecules. These forces are much stronger than the simple van der Waals or dipole-dipole interactions found in the other hydrides, resulting in a higher boiling point that keeps water in the liquid state at standard room conditions.

In the electrolysis of dilute hydrochloric acid (HCl), two anions are present at the anode: chloride ions(Cl\(^-\)) and hydroxide ions (OH\(^-\)) from water. According to the electrochemical series, hydroxide ions are more easily discharged than chloride ions when the solution is dilute. Therefore, the (OH\(^-\)) ions undergo oxidation to produce oxygen gas (O\(_2\)) and water.

The ions F\(^−\),Na\(^+\), Mg\(^{2+}\), Al\(^{3+}\) are isoelectronic species, meaning they all have the same number of electrons (10 electrons). For isoelectronic ions, the ionic size is determined by the nuclear charge (number of protons). As the number of protons increases, the attraction between the nucleus and the electrons becomes stronger, pulling the electrons closer and decreasing the ionic radius. Order of Protons: F\(^−\) = 9 protons (Lowest charge → Largest size Na\(^+\)= 11 protons Mg\(^{2+}\)=12 protons Al\(^{3+}\)= 13 protons (Highest charge → Smallest size) Therefore, the decreasing order of ionic size is F\(^−\), Na\(^+\), Mg\(^{2+}\), Al\(^{3+}\)

The cigarette filter reduces nicotine levels through adsorption, a surface phenomenon where nicotine molecules (the solute) from the smoke (mobile phase) adhere to the surface of the filter material (stationary phase).

Solubility in this context refers to the molar concentration of the saturated solution. Given: Volume of Solution = 25 cm\(^3\) Number of moles of solute, n = 0.02 mole Solubility = ? Solubility = \(\frac{n X 1000}{Volume of solvent}\) = \(\frac{0.02 X 1000}{25}\) = 0.8 moldm\(^{-3}\)