Model Question Paper 2024-25 - XI Chemistry

The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound.

The angular momentum of an electron in the nth orbit is directly proportional to its principal quantum number (n) and is quantized, meaning it can only exist in discrete values.

The maximum number of electrons that a subshell can accommodate is determined by the azimuthal quantum number (l) and is given by 2(2l + 1).

A molecule with a linear shape has all its atoms aligned in a straight line, with a bond angle of 180 degrees.

The equilibrium constant (K) expresses the ratio of products to reactants at equilibrium, with each concentration raised to the power of its stoichiometric coefficient.

A redox reaction involves the transfer of electrons between reactants, resulting in a change in oxidation states.

The functional group in an alcohol is a hydroxyl group (-OH) attached to a carbon atom.

Benzene has 6 sigma bonds and 3 pi bonds, making a total of 12 bonds.

An alkyne is a hydrocarbon containing at least one carbon-carbon triple bond.

Hydrogenation is the process of adding hydrogen gas (H2) to an unsaturated hydrocarbon, converting it into a saturated compound.

The azimuthal quantum number (l) describes the shape of an electron's orbital and its angular momentum. It can have values from 0 to (n-1), where n is the principal quantum number.

The magnetic quantum number (ml) specifies the orientation of an electron's orbital in space. It can have values ranging from -l to +l, including 0.

Ionization enthalpy is the minimum energy required to remove an electron from a gaseous atom or ion in its ground electronic state, forming a cation.

Across a Period: Ionization enthalpy generally increases due to increasing effective nuclear charge and decreasing atomic size. Down a Group: Ionization enthalpy generally decreases due to increasing atomic size and shielding effect.

The first law of thermodynamics states that energy can neither be created nor destroyed in an isolated system; it can only be transformed from one form to another.

The work done during the reversible and isothermal expansion of an ideal gas is calculated using the formula: W = -nRTln(V2/V1), where n is the number of moles, R is the ideal gas constant, T is the temperature, and V1 and V2 are the initial and final volumes, respectively.

The Carius method involves heating a known mass of the organic compound with fuming nitric acid in the presence of silver nitrate. The halogen present in the compound is converted into its silver halide, which is then weighed. The percentage of halogen is calculated based on the weight of the silver halide.

Isomerism is the phenomenon where two or more compounds have the same molecular formula but different structural formulas and properties.

Functional isomers have the same molecular formula but different functional groups.

Alkynes are more acidic than alkanes because the sp hybridized carbon atom in alkynes is more electronegative than the sp3 hybridized carbon atom in alkanes.

The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers.

Hund's rule of maximum multiplicity states that electrons will individually occupy all orbitals within a subshell before doubling up in any one orbital. This minimizes electron-electron repulsion by maximizing electron spin.

Heisenberg's Uncertainty Principle states that it is impossible to simultaneously determine both the position and momentum of a particle with perfect accuracy. The more precisely one is known, the less precisely the other can be known.

Electron gain enthalpy is the change in energy that occurs when an electron is added to a neutral gaseous atom to form a negative ion. It is a measure of the atom's tendency to gain an electron.

The periodic table is a chart of known elements, organized by their atomic number, with similar chemical properties occurring in vertical columns called groups and horizontal rows called periods. Elements in the same group have similar valence electron configurations, resulting in similar chemical behaviors. Periodicity refers to the recurring, repeating patterns in the properties of elements as you move across a period and down a group.

Gibbs free energy (G) is a thermodynamic function that combines enthalpy (H) and entropy (S) to predict the spontaneity of a reaction. It quantifies the amount of energy available for useful work in a thermodynamic system.

The sign of ∆S for the reaction 2Cl(g) → Cl2(g) will be negative. This indicates that the reaction leads to a decrease in entropy or disorder. When two chlorine atoms combine to form a chlorine molecule, the number of particles decreases, leading to a more ordered state.

A catalyst is a substance that speeds up the rate of a chemical reaction without being consumed in the process. It achieves this by providing an alternative reaction pathway with lower activation energy. In the Haber process, the catalyst helps to lower the activation energy of the reaction, making it more efficient at a lower temperature.

The equilibrium constant expression for the Haber process is Kc = [NH3]^2 / [N2][H2]^3. This expression shows the relationship between the concentrations of reactants and products at equilibrium.

The volume occupied by 1 mole of an ideal gas at NTP (Normal Temperature and Pressure) is 22.4 L.

The limiting reagent is the reactant that is completely consumed first in a chemical reaction, thus limiting the amount of product that can be formed.

BH3 is nonpolar because it is a symmetrical molecule with three identical B-H bonds, and the dipole moments of each bond cancel each other out. NH3 is polar because it has a pyramidal shape with a lone pair of electrons on the nitrogen atom, creating an uneven distribution of electron density and a net dipole moment.

Sigma (σ) bonds are formed by the direct overlap of atomic orbitals along the internuclear axis, resulting in a strong, single bond. They are characterized by free rotation around the bond axis. Pi (π) bonds are formed by the lateral overlap of atomic orbitals above and below the internuclear axis, resulting in a weaker, multiple bond. They are characterized by restricted rotation around the bond axis.

Ice floats on water because it is less dense than liquid water. Water molecules are hydrogen-bonded in ice, creating a more open, crystalline structure compared to the more tightly packed molecules in liquid water. This open structure in ice makes it less dense.

Friedel-Crafts alkylation is an electrophilic aromatic substitution reaction where an alkyl group is introduced to an aromatic ring. It involves the use of a Lewis acid catalyst, like AlCl3, to generate a carbocation intermediate that attacks the aromatic ring, creating a new carbon-carbon bond.

Butane can be prepared from ethane by using a series of reactions. First, ethane is chlorinated to form chloroethane. Then, two molecules of chloroethane are reacted in the presence of sodium metal to form butane.

The reaction of calcium carbide (CaC2) with water (H2O) produces acetylene (C2H2) and calcium hydroxide (Ca(OH)2).