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Topic 5: Energetics

カード 23枚 作成者: Yuk0ga (作成日: 2016/06/13)

  • Define the term "heat"

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  • 1

    Define the term "heat"

    補足(例文と訳など)

    答え

    • Heat is the transfer of energy from a higher temperature object to a lower temperature object

    解説

  • 2

    Define the term "temperature"

    補足(例文と訳など)

    答え

    • Temperature is the measure of the average kinetic energy of the particles in a substance.

    解説

  • 3

    Which sample of gas has the highest temperature?

    補足(例文と訳など)

    答え

    • The left one (longer arrows = faster movement)

    解説

  • 4

    What is 0°C in K?

    補足(例文と訳など)

    答え

    • 273K

    解説

  • 5

    Define enthalpy change.

    補足(例文と訳など)

    答え

    • Enthalpy change is the amount of heat absorbed or released in a chemical reaction.

    解説

  • 6

    Define standard enthalpy change of reaction.

    補足(例文と訳など)

    答え

    • The standard enthalpy change of reaction is the enthalpy change under STP conditions (100kPa and 298K)

    解説

  • 7

    Chemical reactions can be classified as 1)________ or 2)________depending on whether heat is absorbed or released.

    補足(例文と訳など)

    答え

    • 1) exothermic 2) endothermix

    解説

  • 8

    Classify the following diagrams as either exothermic or endothermix reaction

    補足(例文と訳など)

    • You should be able to sketch these diagrams.

    答え

    • Left: Exothermic Right: Endothermic

    解説

  • 9

    Exothermic reaction is when heat is ________.

    補足(例文と訳など)

    答え

    • Released

    解説

  • 10

    Endothermic reaction is when heat is _______.

    補足(例文と訳など)

    答え

    • Absorbed

    解説

  • 11

    What is the formula for calculating enthalpy changes?

    補足(例文と訳など)

    答え

    • Q = mcΔT

    解説

  • 12

    What is the specific heat capacity of water?

    補足(例文と訳など)

    答え

    • 4.18(Jg^-1℃^-1)

    解説

  • 13

    What are the two important things that you should remember when using Q=mcΔT?

    補足(例文と訳など)

    答え

    • 1. Put a negative sign to your answer because the reaction is exothermic. 2. The answer should be in kJ/mol^-1. (Divide the answer by 1000 in the end)

    解説

    1. Ex.) 400 cm^3 → ÷1000= 0.400 dm^-3

  • 14

    Define standard enthalpy change of formation (ΔH°f).

    補足(例文と訳など)

    答え

    • ΔH°f is the enthalpy change when one mole of a substance is formed from its elements in their standard states under standard conditions.

    解説

  • 15

    What is the formula for calculating the standard enthalpy change of formation (ΔH°f)?

    補足(例文と訳など)

    答え

    • ΔH = (sum of ΔH°f of products) - (sum of ΔH°f of reactants)

    解説

  • 16

    What are the two important things you should remember when calculating the standard enthalpy change of formation (ΔH°f)?

    補足(例文と訳など)

    答え

    • 1. Elements (such as O2, H2) have a ΔH°f value of zero. 2. You have to multiply the coefficients with the ΔH°f.

    解説

    2. Ex.) 5CO2 → 5×(-394)

  • 17

    What does the Hess's law state?

    補足(例文と訳など)

    答え

    • The enthalpy change for a chemical reaction is independent of the route by which the chemical reaction occurs.

    解説

  • 18

    What are the steps for calculating the enthalpy change with application of the Hess's law?

    補足(例文と訳など)

    答え

    • 1. Adjust the coefficients/position of reactants and products according to the final reaction. 2. Cancel out all the things that are the same on the opposite side of the arrow. 3. Add all the enthalpy changes.

    解説

  • 19

    Define average bond enthalpy

    補足(例文と訳など)

    答え

    • Average bond enthalpy is the energy needed to break one mole of bonds in a gaseous molecule (averaged over similar compounds)

    解説

  • 20

    Is bond breaking endothermic or exothermic?

    補足(例文と訳など)

    答え

    • endothermic (requires energy)

    解説

  • 21

    Is bond making endothermic or exothermic?

    補足(例文と訳など)

    答え

    • exothermic (releases energy)

    解説

  • 22

    What is the formula for calculating the enthalpy change using average bond enthalpies?

    補足(例文と訳など)

    答え

    • ΔH = (sum of the bonds broken) - (sum of the bonds made)

    解説

  • 23

    When we calculated the enthalpy of combustion of methane, it was different from the literature value. What two factors are causing the difference? CH_4(g) + 2O_2(g) → CO_2(g) + 2H_20(l)

    補足(例文と訳など)

    答え

    • 1. Average bond enthalpies are only valid for gases. (liquid is in the equation) 2. The actual value for the specific bond may be different to the average value.

    解説

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