Chemistry Exam - Class 11
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Questions and Answers

What is the main product of the Wurtz reaction?

  • Alcohols
  • Alkenes
  • Alkanes (correct)
  • Alkynes

What happens to ionization enthalpy as we move down a group in the periodic table?

  • Remains constant
  • Decreases (correct)
  • Fluctuates randomly
  • Increases

Which oxidation state is associated with manganese in MnO4-?

  • +5
  • +4
  • +2
  • +7 (correct)

What condition is necessary for a compound to be considered aromatic?

<p>It must be planar (C)</p> Signup and view all the answers

What type of reaction involves the breaking down of a compound using heat?

<p>Cracking (A)</p> Signup and view all the answers

What is the pH of a solution formed by mixing equal volumes of a strong acid with pH 6 and pH 4?

<p>5 (A)</p> Signup and view all the answers

Which hybridization occurs in PCl5?

<p>sp3d (C)</p> Signup and view all the answers

Which statement is true regarding electron gain enthalpy?

<p>It increases from left to right across a period (A)</p> Signup and view all the answers

What is the order of decreasing stability of the following cations: (I) CH3C+ HCH3, (II) CH3C+ HOCH3, and (III) CH3C+ HCOCH3?

<p>I &gt; II &gt; III (B)</p> Signup and view all the answers

Which law is exemplified by the reaction of gases where 45.4 L of dinitrogen reacts with 22.7 L of dioxygen to produce 45.4 L of nitrous oxide?

<p>Avogadro's Law (C)</p> Signup and view all the answers

What is the molarity of a solution prepared by dissolving 82.0 g of CaCl2 in enough water to make 812 mL of solution?

<p>0.61 M (A)</p> Signup and view all the answers

What is the pH of a solution obtained by mixing 50 ml of 1 M HCl and 30 ml of 1 M NaOH?

<p>2 (A)</p> Signup and view all the answers

What is the relationship expressed in the equation ∆U = ∆q + ∆W?

<p>First law of thermodynamics (C)</p> Signup and view all the answers

What should be defined as 'x' in the process of determining equilibrium concentrations?

<p>The concentration of one of the reactants that reacts as equilibrium is approached. (D)</p> Signup and view all the answers

Which of the following accurately describes the relationship between Gibbs energy and reaction spontaneity?

<p>If ∆G &lt; 0, the reaction is spontaneous and proceeds in the forward direction. (D)</p> Signup and view all the answers

What condition indicates that a reaction has achieved equilibrium?

<p>The Gibbs energy change ∆G equals zero. (A)</p> Signup and view all the answers

What happens to the equilibrium constant K if the standard Gibbs energy ∆Gø is negative?

<p>K is greater than one. (D)</p> Signup and view all the answers

What is the correct mathematical expression for Gibbs energy at equilibrium?

<p>∆G = Gø + RT lnK = 0. (B)</p> Signup and view all the answers

How is the reaction quotient Q related to the equilibrium constant K at equilibrium?

<p>Q equals K. (C)</p> Signup and view all the answers

What must be done if a quadratic equation is formed when solving for equilibrium concentrations?

<p>Choose the solution that is positive and makes chemical sense. (D)</p> Signup and view all the answers

Which statement is true about the effect of concentration changes on the value of the equilibrium constant K?

<p>Changes in concentration do not affect K. (A)</p> Signup and view all the answers

What does it imply if ∆Gø > 0?

<p>The reaction is non-spontaneous or barely proceeds. (B)</p> Signup and view all the answers

Which principle is used to predict changes in equilibrium when conditions are altered?

<p>Le Chatelier’s principle (A)</p> Signup and view all the answers

What is the main objective in chemical synthesis as mentioned?

<p>To maximize the conversion of reactants to products. (B)</p> Signup and view all the answers

How does the addition of a reactant affect an equilibrium system according to Le Chatelier’s principle?

<p>Equilibrium shifts towards producing products. (B)</p> Signup and view all the answers

What happens to the equilibrium constant Kc if the initial concentrations are altered?

<p>It remains constant. (D)</p> Signup and view all the answers

What does a change in temperature do to an equilibrium system according to the principles discussed?

<p>It can alter the position of the equilibrium. (B)</p> Signup and view all the answers

In what way does a change in concentration affect an equilibrium mixture?

<p>Equilibrium shifts to minimize the effect of concentration change. (B)</p> Signup and view all the answers

How is ammonia primarily produced in the world?

<p>From the Haber process. (B)</p> Signup and view all the answers

Which of the following pairs of gases contains the same number of molecules?

<p>32 g of O2 and 32 g of N2 (D)</p> Signup and view all the answers

For the reaction N2 + 3H2 ⇌ 2NH3 + heat, which expression correctly relates Kp and Kc?

<p>Kp = Kc (RT) (D)</p> Signup and view all the answers

What effect does increasing pressure have on the equilibrium position of the reaction N2 + 3H2 ⇌ 2NH3?

<p>Shifts the equilibrium to the right (B)</p> Signup and view all the answers

What is the conjugate base of H2PO4?

<p>PO4-3 (A)</p> Signup and view all the answers

Which of the following is not considered a Lewis acid?

<p>NH3 (C)</p> Signup and view all the answers

Which alkene will give acetic acid upon oxidation with potassium permanganate?

<p>2-Butene (C)</p> Signup and view all the answers

What is the correct order of increasing size for the following species?

<p>F- &lt; Al &lt; Na+ &lt; Mg+2 (A)</p> Signup and view all the answers

Which statement correctly defines the ionization energy of an element?

<p>The energy required to remove the outermost electron of an atom of the element (A)</p> Signup and view all the answers

What happens to the reaction if the reaction quotient Qc is less than the equilibrium constant KC?

<p>The reaction moves in the direction of reactants. (A)</p> Signup and view all the answers

According to Le-Chatelier's principle, what effect does adding heat have to a solid-liquid equilibrium if the reaction is endothermic?

<p>It decreases the amount of solid. (B)</p> Signup and view all the answers

What is the relationship between the equilibrium constant for a forward reaction and the equilibrium constant for its reverse reaction?

<p>The reverse reaction's constant is the inverse of the forward reaction's constant. (A)</p> Signup and view all the answers

What is a black body in terms of radiation?

<p>A body that emits and absorbs radiations of all frequencies uniformly. (B)</p> Signup and view all the answers

What does Planck's equation E = hv represent?

<p>The energy of a quantum of radiation in relation to its frequency. (A)</p> Signup and view all the answers

What observation was made during Hertz's experiment regarding the photoelectric effect?

<p>The number of ejected electrons is proportional to the light's intensity. (A)</p> Signup and view all the answers

What concept did Max Planck introduce to describe energy emission and absorption?

<p>The concept of quanta. (B)</p> Signup and view all the answers

What is the value of Planck's constant?

<p>6.626 × 10^-34 Js (A)</p> Signup and view all the answers

Flashcards

Molecules in 16g O2 and 14g N2

Equal number of molecules in 16 grams of O2 and 14 grams of N2 are not present

Kp and Kc for N2 + 3H2 2NH3

The relationship between the equilibrium constants Kp and Kc in the reaction is Kp=Kc(RT)^-2, where R is the ideal gas constant and T is the absolute temperature.

NH3 Product Increase

The product(NH3) increase when pressure increases in the reaction N2 + 3H2 2NH3

Conjugate base of H2PO4-

The conjugate base of H2PO4- is PO4-3.

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Non-Lewis Acid

Ammonia (NH3) is not a Lewis acid.

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Alkenes and Oxidation

Ethylene, on oxidation with potassium permanganate gives only acetic acid.

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Ion Size Increase Order

The order of increasing ion size is F-<Al<Na+<Mg+2

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Ionization Energy Definition

Ionization energy is the energy required to remove the outermost electron from an atom.

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Wurtz reaction

A reaction that uses sodium metal to couple alkyl halides, synthesizing alkanes with an even number of carbons.

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Decarboxylation

Removal of a carboxyl group (-COOH) from a molecule.

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Ionization Enthalpy

Energy needed to remove an electron from a gaseous atom.

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Electronegativity Trend

Increases across a period, decreases down a group in the periodic table.

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Modern Periodic Law

Properties of elements are periodic functions of their atomic numbers.

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Aromatic Compound

Cyclic compound with a conjugated system of pi electrons following Hückel's rule. It shows special stability.

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Formal Charge

Difference between the number of valence electrons in a neutral atom and the number of electrons assigned to that atom in a Lewis structure, based on a set of rules.

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Hybridisation

Combination of atomic orbitals to form new hybrid orbitals with different shapes and energies.

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Equilibrium Concentration

The concentration of reactants and products when the forward and reverse reaction rates are equal, resulting in no net change in concentration.

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Equilibrium Constant (K)

A constant value representing the ratio of product concentrations to reactant concentrations at equilibrium.

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Reaction Quotient (Q)

A value calculated using the concentrations of reactants and products at any given time, not just at equilibrium.

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Gibbs Free Energy (∆G)

A thermodynamic quantity that measures the spontaneity of a reaction.

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Spontaneous Reaction

A reaction that occurs without external intervention and releases free energy.

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Standard Gibbs Free Energy (∆G⁰)

Gibbs Free Energy under standard conditions (usually 1 atm and 298K).

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Equilibrium Equation

An equation that relates the equilibrium constant (K) to the Gibbs Free Energy and reaction conditions

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Calculating Equilibrium Concentrations

Determining concentrations of reactants and products at equilibrium using stoichiometry and equilibrium constant (K).

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∆Gø > 0

Indicates a non-spontaneous reaction, with a very small amount of product formed.

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Equilibrium Constant (K)

A value that represents the ratio of products to reactants at equilibrium.

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Le Chatelier's Principle

Predicts how a change in a reaction's conditions will shift the equilibrium.

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Effect of Concentration Change

Adding or removing a reactant or product at equilibrium will shift the equilibrium towards making more of what was removed or less of what was added.

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Equilibrium Constant (Kc)

Equilibrium constant independent of initial concentrations.

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Haber Process

The industrial method for producing ammonia (NH3).

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Maximum Yield

Optimal conditions (temperature and pressure) to maximize product formation with minimal energy expenditure.

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Effect of Equilibrium Change

Changes in temperature, pressure, or concentration of reactants or products will cause a reaction to shift until the effect is minimized.

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Reaction Quotient (Qc)

A ratio of products to reactants at any point in a reaction, not necessarily at equilibrium.

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Equilibrium Constant (Kc)

A ratio of products to reactants at equilibrium, a constant value for a specific reaction at a given temperature.

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Le Chatelier's Principle

If a stress is applied to a system at equilibrium, the system shifts to relieve the stress.

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Blackbody Radiation

Radiation emitted by an ideal body that absorbs all incident radiation, emitting uniformly across all wavelengths.

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Planck's Quantum Theory

Energy is emitted or absorbed in discrete packets called quanta, proportional to frequency.

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Photoelectric Effect

Emission of electrons from a material when light shines on it.

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Quantum of Energy

The smallest unit of energy that can be emitted or absorbed.

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Planck's Constant

The proportionality constant relating energy to frequency in Planck's equation.

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Equilibrium Constant (Kc)

A constant value representing the ratio of product concentrations to reactant concentrations at equilibrium in a chemical reaction.

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pH calculation (HCl + NaOH)

Calculate the pH of a solution by mixing known volumes and concentrations of strong acid and base.

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Resonating structure (CO2-2, SO4-2)

Different ways to represent the arrangement of electrons in a molecule, contributing to the overall structure and stability of the molecule.

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Stability of cations (CH3C+)

Determine the order of decreasing stability of cations based on factors affecting carbocation stability.

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Standard enthalpy of combustion

The enthalpy change that accompanies the complete combustion of one mole of a substance under standard conditions.

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Study Notes

Chemistry Exam - Class 11

  • General Instructions:

    • 35 questions, internal choice available
    • Section A: 19 multiple choice questions (1 mark each)
    • Section B: 5 very short answer questions (2 marks each)
    • Section C: 6 short answer questions (3 marks each)
    • Section D: 2 case-based questions (4 marks each)
    • Section E: 3 long answer questions (5 marks each)
    • Use of log tables and calculators is not allowed

  • Section A (Multiple Choice):

    • Question 1: 16 g of O₂ and 14 g of N₂ have the same number of molecules.
    • Question 2: Kp = Kc (RT)¹ for N₂ + 3H₂ = 2NH₃ + heat
    • Question 3: Increasing pressure increases the product in the reaction N₂ + 3H₂ → 2NH₃

  • Section A Further Questions:

    • Question 4: Conjugate base of H₂PO₄⁻ is PO₄³⁻
    • Question 5: NH₃ is not a Lewis acid
    • Question 6: Hydrocarbon formula C₈H₁₀ with given hybridization (sp³, sp², sp², sp³, sp², sp², sp, sp)
    • Question 7: CH₄ + Cl₂ → CH₃Cl + HCl is a substitution reaction.
    • Question 8: CH₃-CH₂-Cl with alc.KOH → CH₃CHO
    • Question 9: 2-Butene gives only acetic acid on oxidation with potassium permanganate

  • Section B (Very Short Answer):

    • Question 10: Calculate average atomic mass of hydrogen using isotope data.
    • Question 11: Calculate work done on ideal gas in compression
    • Question 12: Predict stages of reaction based on Kc and Qc values

  • Section C (Short Answer):

    • Question 12, OR: Difference between Mendeleev and Modern Periodic Law.
    • Question 25 a, b, OR: Explanation of electronegativity increase/ionization enthalpy decrease trends.

  • Section D (Case-Based):

  • Section E (Long Answer):

    • Question 29, OR: Define ionization enthalpy and electron gain enthalpy.
    • Question 30: Describe equilibrium reactions in relation to Qc and Kc, calculations for equilibrium concentrations.
      • Calculate the equilibrium constant, Qc.
      • Comparing Qc to Kc to determine the direction of the reaction (left to right, right to left, or at equilibrium)
    • Question 31: Derive relationships and solve problems related to the equilibrium constants and Gibbs energy. (Details provided in OCR)

  • Additional Topics/Concepts:

    • Calculations for pH, oxidation states, disproportionation, hybridisation
    • Types of reactions (addition, elimination, substitution)
    • Terms like Nucleophile, Electrophile and IUPAC nomenclature
    • Principles like Le Chatelier's principle
    • Law of Conservation of Mass (related to the problem mentioning the reaction, in which 45.4L of N2 and 22.7 L of O2 reacted)
    • Mole fraction calculations

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Description

This quiz consists of 35 questions covering various topics in Chemistry for Class 11 students. It includes multiple choice questions, short answer questions, and long answer questions to assess your understanding of chemical concepts and equations. Prepare to put your knowledge to the test with internal choices available in the exam format.

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