Chemistry Enthalpy and Reaction Quiz
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Questions and Answers

What is the correct enthalpy of formation of ethanol, C2H5OH in KJ/mol?

  • -246 (correct)
  • +246
  • -1646
  • +1646

    • When burning 1.00kg of hydrogen completely under standard conditions, what is the enthalpy change in KJ?

  • -1.43 x 10^5 (correct)
  • +1.43 x 10^5
  • -7.1 x 10^5
  • +7.1 x 10^5

    • What is the value of the heat of reaction per mole of acid when mixing equal volumes of HCl and NaOH at standard conditions?

  • >100 kJ/mol
  • 54 kJ/mol (correct)
  • 670 kJ/mol
  • 1300 kJ/mol

    • Which conditions guarantee that a spontaneous reaction will occur at any temperature?

    <p>∆H is negative and ∆S is positive</p> Signup and view all the answers

    What is the electron affinity of chlorine based on the provided data?

    <p>-362 KJ/mol</p> Signup and view all the answers

    Calculate the value of ∆Gθ for the reaction Mg(s) + H2O(g) → MgO(s) + H2(g) at 373K.

    <p>-312 KJ/mol</p> Signup and view all the answers

    What is the value of ∆H for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) using bond energies?

    <p>-88 KJ/mol</p> Signup and view all the answers

    What does the enthalpy change for the reaction F2(g) → 2F(g) represent?

    <p>½ bond dissociation energy</p> Signup and view all the answers

    How many moles of calcium hydroxide will be neutralized by 2 moles of hydrochloric acid?

    <p>1.0</p> Signup and view all the answers

    What is the concentration of the acid if 25.0ml of it neutralizes 10ml of 0.200 M sodium hydroxide?

    <p>0.160 M</p> Signup and view all the answers

    What is the percent purity of a sample of impure magnesium hydroxide that required 39.3ml of 1.00 mol/L hydrochloric acid for titration?

    <p>95</p> Signup and view all the answers

    What is true about the titration of ethanoic acid with sodium hydroxide?

    <p>The starting pH is below 11</p> Signup and view all the answers

    What is the concentration of Iron (II) sulphate if 25.0ml of the solution required 19.8ml of 0.02 mol/L Potassium (VII) manganate for oxidation?

    <p>0.0158 mol/L</p> Signup and view all the answers

    What is the percentage purity of a piece of iron wire weighing 0.5512g, converted to Fe+2, after titration with potassium dichromate?

    <p>99.50</p> Signup and view all the answers

    For an indicator that changes color at pH 10, which titrations are appropriate?

    <p>I and IV</p> Signup and view all the answers

    What is the molar mass of a monoprotic acid (HA) if 0.384g is neutralized by 30.0ml of 0.100M NaOH?

    <p>81.0 g/mol</p> Signup and view all the answers

    What is the enthalpy change for the combustion of liquid benzene C6H6(l)?

    <p>-371 KJ/mol</p> Signup and view all the answers

    What fraction of A would remain at equilibrium for the reaction A + B ⟷ 2C if Keq is 16?

    <p>2/3</p> Signup and view all the answers

    What is the equilibrium constant Keq for the reaction CH3COOH + C2H5OH ⟷ CH3COOC2H5 + H2O if 0.350 mol of CH3COOH remains?

    <p>2.27</p> Signup and view all the answers

    In a 0.1 M solution of a weak acid HA with pH=4, what is the value of the ionization constant, Ka?

    <p>1 x 10^-6</p> Signup and view all the answers

    What is the hybridization of the starred carbon atom in the provided molecule?

    <p>sp2</p> Signup and view all the answers

    What is the molar concentration of H2(g) in the equilibrium mixture for CO(g) + H2O(g) ⟷ CO2(g) + H2(g) if Kc= 4.0?

    <p>1.0 M</p> Signup and view all the answers

    What is the molecular geometry of H3O+?

    <p>trigonal pyramidal</p> Signup and view all the answers

    Which of these carboxylic acids has the highest strength based on their Ka values?

    <p>Phosphoric acid</p> Signup and view all the answers

    Which molecule adopts a seesaw shape?

    <p>SF4</p> Signup and view all the answers

    Which shape is associated with the molecule XeF4?

    <p>Square planar</p> Signup and view all the answers

    According to the Bronsted-Lowry concept, which substances act as acids in the reaction H2O + CO32- ⟷ HCO3- + OH-?

    <p>H2O and CO32-</p> Signup and view all the answers

    Which factor affects the magnitude of the equilibrium constant?

    <p>Changing the temperature</p> Signup and view all the answers

    Which orbital overlap does NOT result in a sigma bond?

    <p>P and P in this orientation</p> Signup and view all the answers

    Which observation explains why an endothermic reaction is non-spontaneous at 50°C but becomes spontaneous at 200°C?

    <p>Entropy increases with higher temperature.</p> Signup and view all the answers

    What occurs when a catalyst is added to a reaction mixture?

    <p>Provides a new pathway for the reaction</p> Signup and view all the answers

    Which statement regarding acid-base titration is incorrect?

    <p>The equivalence point is always at pH=7.</p> Signup and view all the answers

    What is the rate law for the reaction 3A(g) + 2B(g) → 2C(g) + 2O(g) based on the given trials?

    <p>Rate=K[A]2[B]2</p> Signup and view all the answers

    If the half-life of SOCl2 is 4.1 hours, how long does it take for its concentration to drop from 0.36 M to 0.045 M?

    <p>33 hr</p> Signup and view all the answers

    Given the rate constant of 4.65 L mol-1 s-1, what is the overall order of the reaction?

    <p>Third</p> Signup and view all the answers

    After 100 minutes, how many molecules remain unreacted if a first-order reaction starts with 1.00 x 10^20 molecules?

    <p>3.20 x 10^16 molecules</p> Signup and view all the answers

    Which of the following statements about the rate equation for a reaction is incorrect?

    <p>The rate equation for a reaction 2A + B → C must be rate=k[A]2[B]</p> Signup and view all the answers

    What are the appropriate units for a third-order rate constant?

    <p>L2 mol-2 s-1</p> Signup and view all the answers

    What type of bonds are present in the triple bond of ethyne (C2H2) according to valence bond theory?

    <p>One σ bond and two π bonds</p> Signup and view all the answers

    Which of the following statements about atomic orbitals is incorrect?

    <p>The nitrogen atom in NH3 is sp2 hybridized</p> Signup and view all the answers

    Study Notes

    Titration Calculations and Concepts

    • Neutralization Reactions: Hydrochloric acid neutralizes calcium hydroxide. 2 moles of hydrochloric acid neutralize 1 mole of calcium hydroxide.
    • Acid Concentration: 25.0 mL of an unknown acid neutralizes 10 mL of 0.200 M sodium hydroxide solution. Calculate the unknown acid's concentration.
    • Impure Substance Titration: A 1.2g sample of impure magnesium hydroxide needs 39.3 mL of 1.00 mol/L hydrochloric acid for complete neutralization. Calculate the percentage purity of the sample.
    • Titration with Ethanoic Acid: Titration using ethanoic acid and sodium hydroxide, the starting pH is below 11, the equivalence point is below 7, and the finishing pH is approximately 7.
    • Iron (II) Sulphate Oxidation: 25.0 mL of Iron (II) sulphate solution required 19.8 mL of 0.02 mol/L Potassium (VII) manganate for complete oxidation. Solve for the concentration of the Iron (II) sulphate solution.
    • Iron Wire Purity: A 0.5512g iron wire sample, when titrated with 40.8 mL of 0.0400 mol/L potassium dichromate, reaches its endpoint with Cr+3 and Fe+2 products. Solve for the percentage purity.

    Monoprotic Acid Molar Mass

    • Molar Mass Determination: A 0.384g sample of monoprotic acid (HA) requires 30.0 mL of 0.100M NaOH for complete titration at its equivalence point. Determine the molar mass of HA.

    Combustion and Heat Release

    • Carbon Combustion: Burning 3g of carbon releases 98.5 kJ of heat to form carbon dioxide. Calculate the heat released for 2.00 moles of CO2 production.
    • Endothermic Reactions and Heat Capacity: An endothermic reaction lowers the temperature of 500 mL of water by 3K. The heat capacity of the calorimeter is 10 J/K. Calculate the heat absorbed by the reaction and remember to account for water's specific heat capacity (4.18 J/(g K)).

    Formation Enthalpy and Enthalpy Change

    • Ethanol Formation Enthalpy: Determine the enthalpy of formation of ethanol, using combustion data, in KJ/mol.
    • Standard Enthalpy of Formation of Water: The Standard enthalpy of formation of water is -286 KJ/mol. Find the enthalpy change, in KJ, when 1.00 kg of hydrogen is completely burned under standard conditions.

    Titration, Indicators, and Equilibrium

    • Indicator Color Change: An indicator changes color at pH 10. Discuss which titrations could potentially utilize this indicator.
    • Equilibrium Constant and Fractions: Keq for a reaction A + B \rightarrow 2C. Calculate the fraction of reactant A remaining at equilibrium, given that the equilibrium constant is 16.

    Acid-Base Equilibrium Constants

    • Ionization Constant Determination: A weak acid (HA) solution with pH of 4. Determine the acid ionization constant (Ka) given a concentration of 0.1 M.
    • Equilibrium Concentration: A mixture of 2.0 mol of CO(g) and 2.0 mol H2O(g) in a 1 L flask at high temperature, if the equilibrium constant Kc = 4.0. Find the molar concentration of H2(g) in the equilibrium mixture.

    Reaction Order, Rate Laws, and Mechanisms

    • Rate Law for Reaction X + Y → 2Z: A reaction mechanism with two steps determines the rate law for the reaction. The mechanism given was 1) X + Y → I (slow), and 2) I + 2Z → P (fast) and derive the rate equation.
    • Rate Law Determination: Determine the rate law, given the initial concentration of reactants ([A] and [B]) and the rate of formation of product ([C]).
    • First Order Decomposition: A first order reaction, SOCL2, has a half-life of 4.1 hr. Calculate the time required for the concentration of SOCL2 to drop from 0.36 M to 0.045 M.
    • Reaction Order: Calculate the order of the reaction, given the rate constant (4.65 L mol-1 s-1).
    • First Order Reaction and Molecule Count: A first-order reaction with a half-life of 20.0 minutes starts with 1.00 x 1020 molecules of reactant at time t = 0. Find how many molecules remain unreacted after 100.0 minutes.

    Bond Theory and Molecular Orbitals

    • Electron affinity of Chlorine: Determine the electron affinity of Chlorine, given several thermodynamic data related to potassium and potassium chloride.
    • Hybridization and Geometries: Discuss the hybridization of atomic orbitals, including the carbon atom in C2H2, the nitrogen atom in NH3, and the given molecule with an asterisk on the carbon atom. Explain the geometries associated with each.

    Additional Chemical Concepts

    • Enthalpy Changes: Explain enthalpy changes using bond energies and provide examples.
    • Acid Strength: Differentiate between various acids (formic acid, citric acid, sulphurous acid, phosphoric acid) based on their Ka values and determine the strongest acid from the given data.
    • Equilibrium Effects: Discuss how different factors (adding reactant, catalyst, changing temperature, removing products, etc) affect the magnitude of equilibrium constant.
    • Reaction Mechanism: Describe the different possible reaction mechanisms related to reaction rate and associated calculations.

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    Description

    Test your knowledge on enthalpy of formation, reaction spontaneity, and electron affinity with this chemistry quiz. Explore various scenarios including the burning of hydrogen and acid-base neutralization reactions. Ideal for students studying thermodynamics and chemical reactions.

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