Thermochemistry Basics
24 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the First Law of Thermodynamics primarily state?

  • Heat energy always moves from cold to hot.
  • Energy cannot be created or destroyed. (correct)
  • Potential energy is the only form of energy considered.
  • Chemical reactions release all energy as heat.

    • Which component contributes to heat transfer during a chemical reaction?

  • The change in enthalpy during the reaction. (correct)
  • The distance between reactant molecules.
  • The color of the reactants.
  • The pressure of the system.

    • For the combustion of octane, which process releases energy?

  • Breaking the bonds of the reactants.
  • Increasing the pressure in the reaction vessel.
  • Cooling the products after formation.
  • Forming the bonds of the products. (correct)

    • How much energy is required to heat a 125 g piece of zinc from 23 °C to 125 °C?

    <p>62.25 J</p> Signup and view all the answers

    Which liquid among the following requires the most energy to reach its boiling point?

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

    What specific heat results from mixing a 65.39 g aluminum pellet at 80.0 °C with 500 g of water?

    <p>0.41 J/g ºC</p> Signup and view all the answers

    When thermal equilibrium is reached, what happens to the temperatures of the substances involved?

    <p>The temperatures equalize at a new intermediate temperature.</p> Signup and view all the answers

    What is the specific heat of water, used in calculations for thermal processes?

    <p>4.184 J/g ºC</p> Signup and view all the answers

    What is the specific heat of the solution used in the calorimetry experiments?

    <p>4.22 J/g ºC</p> Signup and view all the answers

    During the calorimetry experiments, which type of calorimeter is primarily used for measuring reactions at constant pressure?

    <p>Coffee cup calorimeter</p> Signup and view all the answers

    In the dissolution of 10.0 g of NaOH, what is the sign of ΔrH° indicating the reaction's nature?

    <p>Exothermic reaction</p> Signup and view all the answers

    What is the initial temperature of the ammonia solution before mixing with acetic acid?

    <p>21.6 ºC</p> Signup and view all the answers

    What is the mass of water considered in the combustion of 3.50 g of FAME biofuel?

    <p>1.00 kg</p> Signup and view all the answers

    What was the temperature change observed in the copper metal reaction with nickel(II) nitrate?

    <p>0.6 ºC decrease</p> Signup and view all the answers

    How much energy is released when 10.0 g of NaNO3 dissolves in water with a ΔrH° of 20.5 kJ/mol?

    <p>2.0 kJ</p> Signup and view all the answers

    What is the enthalpy of combustion for a sample if the temperature of the calorimeter reached 32.73 °C and the starting temperature was 23.00 °C?

    <p>5.26 kJ/g</p> Signup and view all the answers

    What is the standard reaction enthalpy (ΔrHº) for the reaction 2 S (g) + 3 O2 (g) → 2 SO3 (g) using Hess's Law?

    <p>-594</p> Signup and view all the answers

    Which step is necessary to determine the enthalpy for the reaction W (s) + C (s) → WC (s)?

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

    How does Hess's Law contribute to calculating the overall reaction enthalpy?

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

    Using the provided enthalpies of formation, what is the standard reaction enthalpy for the reaction CaO (g) + H2O (l) → Ca(OH)2 (s)?

    <p>-410.3</p> Signup and view all the answers

    In calculating the reaction enthalpy for combustion of naphthalene (C10H8), what is the enthalpy of formation for CO2?

    <p>-394</p> Signup and view all the answers

    What role do standard enthalpies of formation play in determining overall reaction enthalpy?

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

    When using Hess's Law, what is the result if a reaction is reversed?

    <p>1</p> Signup and view all the answers

    How do variations in the enthalpies of formation affect the calculated enthalpy of a reaction?

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

    Study Notes

    Thermochemistry

    • The first law of thermodynamics, energy cannot be created or destroyed
    • Energy is the ability to do work or transfer heat
    • Energy is always conserved
    • Isolated system does not exchange energy with the surroundings

    Heat

    • The amount of heat transferred is directly proportional to the change in temperature and the mass of the substance
    • The amount of heat transferred is related to the specific heat of the substance
    • Specific heat is the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius
    • For a given temperature change, a substance with a lower specific heat requires less heat to undergo the same change

    Enthalpy

    • Enthalpy is the heat content of a system at constant pressure
    • Enthalpy change is the change in heat content of a system during a chemical reaction
    • The sign of the enthalpy change indicates whether heat is released or absorbed
    • Negative enthalpy change indicates heat is released from the system (exothermic)
    • Positive enthalpy change indicates heat is absorbed by the system (endothermic)

    Calorimetry

    • Calorimetry is the study of heat transfer
    • Calorimeters are used to measure the heat transferred during a chemical reaction
    • There are two main types of calorimeters: constant pressure calorimeters and constant volume calorimeters
    • Constant pressure calorimeter: a device that measures the heat transferred at constant pressure
    • Constant volume calorimeter: a device that measures the heat transferred at constant volume

    Hess's Law

    • Hess's Law states that the enthalpy change of a reaction is independent of the pathway
    • The enthalpy change of a reaction is equal to the sum of the enthalpy changes of the individual steps in the reaction
    • Hess's Law is used to calculate the enthalpy change of a reaction that cannot be measured directly

    Standard Enthalpy of Formation

    • The standard enthalpy of formation (∆fHº) of a compound is the enthalpy change when 1 mole of the compound is formed from its elements in their standard states
    • The standard enthalpy of formation of an element in its standard state is zero
    • The standard enthalpy of formation can be used to calculate the enthalpy change of a reaction

    Bond Energies

    • Bond energy is the energy required to break a bond between two specific atoms
    • Bond energies can be used to estimate the enthalpy change of a reaction
    • Bond energy is a measure of the strength of a bond

    State Functions

    • A state function is a property that depends only on the initial and final states of a system, not on the pathway
    • Enthalpy is a state function
    • Internal pressure is a state function
    • Entropy is a state function
    • Volume is a state function

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Chapter 5 Thermochemistry PDF

    Description

    This quiz covers the fundamental concepts of thermochemistry, including the first law of thermodynamics, heat transfer, and enthalpy. Understand how energy conservation, specific heat, and enthalpy changes influence chemical reactions. Test your knowledge on how these principles apply to real-world scenarios.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser