Worksheet: Units of Energy

In this worksheet, we will practice using the Faraday constant to convert between units of electron volts and joules per mole.

Q1:

Aqueous copper(II) ions react with metallic zinc to produce aqueous zinc(II) ions and metallic copper: In this reaction, two electrons are transferred per copper(II) ion and 1.099 eV of energy is released per transferred electron. Calculate in millimoles the number of moles of copper ions that must react every second to produce a power output of 50.0 W.

Q2:

The voltage across a tungsten wire is 13.50 V. The wire weighs 50.0 mg and requires 171 kJ/mol of energy to melt completely. Assuming that the wire is well insulated and the voltage across the wire does not change, calculate the minimum number of electrons that must pass through the wire for complete melting to take place.

  • A 3 . 9 2 × 1 0 2 0
  • B 2 . 1 6 × 1 0 1 8
  • C 9 . 9 4 × 1 0 1 8
  • D 2 . 1 5 × 1 0 1 9
  • E 5 . 5 2 × 1 0 1 9

Q3:

Light with an energy of 2.254 eV per photon is absorbed by a solar cell with an efficiency of 23.2%. How many moles of photons must be absorbed each day to produce an average power output of 19.0 W?

Q4:

The potential difference across a lamp is 6.000 V. How many joules of energy are supplied to the bulb per electron?

  • A 1 . 0 4 0 × 1 0 1 8 J
  • B 3 . 7 4 5 × 1 0 1 9 J
  • C 2 . 6 7 0 × 1 0 2 0 J
  • D 9 . 6 1 3 × 1 0 1 9 J
  • E 2 . 2 4 7 × 1 0 2 0 J

Q5:

If 0.153 moles of electrons move across a potential difference of 53.0 V, how much energy is transferred in joules?

  • A 5 . 1 1 × 1 0 6 J
  • B 3 . 1 9 × 1 0 5 J
  • C 1 . 1 9 × 1 0 4 J
  • D 7 . 8 2 × 1 0 5 J
  • E 6 . 3 1 × 1 0 4 J

Q6:

The power output of the Sun is 3 . 8 4 6 × 1 0 2 6 W. In electron volts, how much energy is released by the Sun every 5.00 minutes?

  • A 2 . 8 8 × 1 0 4 6 eV
  • B 1 . 8 5 × 1 0 2 9 eV
  • C 4 . 6 2 × 1 0 2 7 eV
  • D 7 . 2 0 × 1 0 4 7 eV
  • E 2 . 8 8 × 1 0 4 7 eV

Q7:

Hydrolysis of one molecule of adenosine triphosphate (ATP), the energy source of biological cells, releases 0.352 eV of energy. By contrast, the energy released by the combustion of 1.00 kg of coal is 32.5 MJ. Calculate the number of moles of ATP needed to release the same energy as the combustion of 12.8 kg of coal.

  • A 1 . 5 2 × 1 0 3 mol
  • B 1 . 4 4 × 1 0 4 mol
  • C 1 . 1 4 × 1 0 3 mol
  • D 1 . 2 2 × 1 0 4 mol
  • E 1 . 8 9 × 1 0 4 mol

Q8:

The fission of one atom of uranium-235 releases 202.5 MeV of energy. If the average power consumption of a city is 1 . 2 0 × 1 0 4 MW, calculate the number of fissions of atoms of uranium-235 needed to power the city for 1.00 hour.

  • A 5 . 4 6 × 1 0 2 4
  • B 1 . 7 3 × 1 0 2 2
  • C 2 . 2 2 × 1 0 2 2
  • D 1 . 3 3 × 1 0 2 4
  • E 5 . 3 3 × 1 0 2 3

Q9:

A concentration gradient of calcium ions produces a potential of 146 mV across a cell membrane. Calculate, in kilojoules per mole, the minimum energy required by the cell to generate this concentration gradient.

Q10:

Electrolysis of 1.00 kg of aluminum oxide to produce solid aluminum requires a minimum energy input of 1 . 6 4 × 1 0 4 kJ. Calculate, in electron volts, the minimum energy required for this reaction per atom of solid aluminum produced.

Q11:

What is the voltage of a battery that supplies 511 kJ of energy per mole of electrons?

Q12:

Which of the following is the best definition of an electron volt (eV)?

  • AThe energy transferred by one mole of electrons moving across a potential difference of 1 V
  • BThe energy transferred by one coulomb of electrons moving across a potential difference of 1 V
  • CThe voltage generated by the ionization of one mole of ground-state hydrogen atoms
  • DThe energy transferred by one electron moving across a potential difference of 1 V
  • EThe voltage generated by the ionization of one ground-state hydrogen atom

Q13:

Relative to a free electron, the potential energy of the electron in a hydrogen atom is 1 3 . 6 0 6 eV. Express this value to 4 significant figures in units of joules.

  • A 2 . 2 5 9 × 1 0 1 9 J
  • B 8 . 4 9 2 × 1 0 1 9 J
  • C 3 . 4 9 3 × 1 0 1 8 J
  • D 2 . 1 8 0 × 1 0 1 8 J
  • E 4 . 5 8 7 × 1 0 1 8 J

Q14:

The bond energy of a typical C C single bond is 348 kJ/mol. Calculate, in electron volts, the potential energy of one electron in this bond relative to the valence electron of an isolated C atom.

Q15:

Nitric oxide ( N O ) is formed when nitrogen and oxygen react within a lightning bolt. If a lightning bolt produces 150 kg of N O and the reaction consumes a total of 360 MJ of energy, calculate, in electron volts, the energy required for the formation of one N O molecule.

Q16:

One electron in a typical I I single bond has a potential energy of 0 . 7 7 2 eV relative to the valence electron of an isolated I atom. Calculate, in kilojoules per mole, the bond energy of the I I bond.

Q17:

The total molar bond energy of O 2 is 498 kJ/mol and the molar O O 𝜎 bond energy is 146 kJ/mol. Calculate in eV the energy of one O O 𝜋 bond.

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