The number of formula units in 29.25g of common salt_________________?
Correct answer: B. 3.01 x 10^23
- A. 6.022 x 10^23
- B. 3.01 x 10^23
- C. 2 x NA
- D. 4 x 6.022 x 10^23
Explanation
The molar mass of NaCl is 23.0 g/mol + 35.5 g/mol = 58.5 g/mol. Thus 29.25 g ÷ 58.5 g/mol = 0.5 mol, and 0.5 mol x 6.022 x 10^23 formula units/mol = 3.011 x 10^23 formula units, approximately 3.01 x 10^23; option a is the common mistake of using 1 mole instead of 0.5 mole.
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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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