Chemistry 141

Subdecks (1)

Cards (242)

  • More Practice !!

    aq + H2 (g) → MnO2 + 4 HCl → MnCl2 + Cl2 + 2 H2O
  • Chapter 10 - Thermochemistry
    2 NH4NO3 (s) → 2 N2 (g) + O2 (g) + 4 H2O (g)
  • Conversion Between Energy Units
    Conversion between different units of energy
  • First Law of Thermodynamics

    Thermodynamics is the study of energy and its interconversions. The total amount of energy in the universe is constant; it is conserved.
  • System
    The area or location under study
  • Surroundings
    Area or location outside the system
  • Universe
    System + surroundings
  • Endothermic
    Heat transfers from surroundings to the system
  • Exothermic
    Heat transfers from the system to the surroundings
  • State Function
    Regardless of the trail, when you reach the top, you will be 10,000 ft above the base
  • ΔE and ΔH

    Are state functions
  • q and w

    Are not state functions
  • Energy Exchange

    E = w + q
  • Work
    Transfer of energy by motion (macroscopic objects)
  • Heat
    Transfer of thermal energy (vibration of atoms/molecules)
  • Heat
    The exchange of thermal energy between a system and its surroundings
  • Temperature
    The measure of thermal energy in a system
  • Specific Heat Capacity

    Measure of a substance's intrinsic ability to absorb heat. The specific heat capacity is the amount of heat energy required to raise the temperature of one gram of a substance 1 °C.
  • Example
    A Cu block of unknown mass has an initial temperature of 65.4°C. It is immersed in a beaker of water (m=95.7 g) at 22.7°C. The two substances reach thermal equilibrium at 24.2°C. What is the mass of the copper? (Cs,Cu = 0.385 J/g·K)
  • Pressure–Volume Work

    PV work is work caused by a volume change against an external pressure. w = –PΔV. Units of w (atm·L)
  • Bomb Calorimeter

    w = –PΔV because ΔV=0 (constant volume) so w=0. ΔErxn = wrxn + qrxn. ΔErxn = qrxn (change in energy equals heat of reaction). qcal = -qrxn. qcal = Ccal x ΔT
  • Heat
    The exchange of thermal energy between a system and its surroundings
  • Temperature
    The measure of thermal energy in a system
  • Thermal properties

    • Hot
    • Cold
    • Net heat transfer
  • Specific Heat Capacity

    • Measure of a substance's intrinsic ability to absorb heat
    • The amount of heat energy required to raise the temperature of one gram of a substance 1°C
  • The specific heat of copper is 0.385 J/(g·°C)
  • Calculating heat changes

    1. Heat (J)
    2. Specific Heat Capacity
    3. Change in temperature (°C)
    4. Mass (g)
  • PV work

    Work caused by a volume change against an external pressure
    w = -PΔV
  • Bomb Calorimeter

    w = -PΔV because ΔV=0 (constant volume), so w=0
    ΔE_rxn = q_cal = -q_rxn
    q_cal = C_cal x ΔT
  • Enthalpy (ΔH)

    Heat of Reaction
    ΔH is the amount of heat absorbed or released by a reaction at constant pressure
    If ΔH is positive: endothermic
    If ΔH is negative: exothermic
  • Constant Pressure Calorimetry

    q_cal = -q_rxn
    q_cal = mass_sol x C_s, sol x ΔT
    ΔH = q_cal (At constant pressure)
  • Comparing ΔH with ΔE

    If moles of gas reactants = moles of gas products, then ΔH = ΔE
    Otherwise, ΔH = ΔE + PΔV
  • Hess's Law
  • ∆Erxn
    Change in internal energy of a reaction
  • ∆V=0
    Therefore w=0
  • Bomb Calorimeter
    Used for solid reactants
  • Enthalpy (∆H)
    Heat of Reaction
  • ∆H
    Amount of heat absorbed or released by a reaction at constant pressure
  • Constant Pressure Calorimetry

    qcal = -qrxn
    qcal = mass sol x Cs, sol x ∆T
  • Example
    50.0 g 0.200 M NaCl(aq) at 24.1 °C is added to 100.0 g of 0.100 M AgNO3(aq) at 24.1 °C in a calorimeter, the temperature increases to 25.2 °C as AgCl(s) forms
    Calculate the approximate amount of heat in joules produced