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General Chemistry: Energy, Thermodynamics, and Calorimetry

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  • What is kinetic energy?

    Kinetic energy is the energy associated with the motion of an object.

  • What is potential energy?

    Potential energy is the energy associated with the position or arrangement of an object.

  • Write the expression for the change in energy (ΔE) of a system doing work on the surroundings and losing heat.

    ΔE = q + w, where both q (heat) and w (work) are negative because the system loses heat and does work on the surroundings.

  • What is the sign convention for heat (q) and work (w) in thermodynamics?

    q is positive if heat is absorbed by the system, negative if released; w is positive if work is done on the system, negative if done by the system.

  • How do you calculate specific heat capacity (c) from heat (q), mass (m), and temperature change (ΔT)?

    Use the formula \(q = m c \Delta T\) and rearrange to \(c = \frac{q}{m \Delta T}\).

  • Convert 59.3 kJ to Joules.

    59.3 kJ = 59300 J (since 1 kJ = 1000 J).

  • Calculate the temperature change (ΔT) if temperature rises from 298 K to 398 K.

    ΔT = 398 K - 298 K = 100 K.

  • How to calculate moles of ethanol burned from mass and molar mass?

    Moles = mass / molar mass; for ethanol, moles = 21.8 g / 46.07 g/mol.

  • How to calculate heat released by a reaction using moles and ΔH°rxn?

    Heat released = moles × ΔH°rxn (use correct sign and units).

  • How to find the heat capacity of a calorimeter from heat released and temperature change?

    Heat absorbed by calorimeter = heat released by reaction; use \(q = C \Delta T\) and solve for C.

  • Calculate moles of PCl3 from 612 g and molar mass 137.32 g/mol.

    Moles = 612 g / 137.32 g/mol.

  • How to determine reaction equivalents for PCl3 in the reaction 4 PCl3 → products?

    Reaction equivalents = moles of PCl3 / 4 (since 4 moles PCl3 per reaction).

  • Calculate energy required for decomposition using reaction equivalents and ΔH°rxn.

    Energy required = reaction equivalents × ΔH°rxn (where ΔH°rxn = +1207 kJ).

  • What is the first law of thermodynamics formula?

    ΔE = q + w, where ΔE is change in internal energy, q is heat, and w is work.

  • What does a negative value of q indicate?

    A negative q means the system is releasing heat to the surroundings.

  • What does a negative value of w indicate?

    A negative w means the system is doing work on the surroundings.

  • What is the molar mass of ethanol (C2H5OH)?

    The molar mass of ethanol is 46.07 g/mol.

  • What is the enthalpy change (ΔH°rxn) for the combustion of ethanol given?

    ΔH°rxn = -1235 kJ for the combustion of ethanol.

  • What is the balanced chemical equation for ethanol combustion given?

    C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g)

  • What is the balanced chemical equation for PCl3 decomposition given?

    4 PCl3(g) → P4(s) + 6 Cl2(g)