The mass of decimole of electrons (NA) is___________________?
Correct answer: C. 0.054 mg
- A. 1.008 mg
- B. 0.184 mg
- C. 0.054 mg
- D. 5.4 mg
Explanation
The mass of one electron is about 9.11 x 10^-31 kg, so the mass of 0.1 mol of electrons is 0.1 x 6.022 x 10^23 x 9.11 x 10^-31 kg = 5.49 x 10^-8 kg. Since 1 kg = 10^6 mg, this is 5.49 x 10^-2 mg = 0.0549 mg, approximately 0.054 mg. The likely mistake is choosing d by using the mass of a full mole of electrons instead of a decimole, which is 0.1 mol.
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About Moles and Avogadro's Number
The mole connects the microscopic number of particles with measurable mass, using Avogadro's number, 6.022 × 10²³ particles per mole. Questions involve molar mass, conversion between mass, moles and particles, percentage composition, empirical and molecular formulas, and distinguishing atoms, molecules, ions and formula units.
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