Which one of the following contains the greatest number of atoms :
Correct answer: C. 71 g of chlorine
- A. 4g of hydrogen
- B. 4g of magnesium
- C. 71 g of chlorine
- D. 127 g of iodine
Explanation
Now let's calculate the number of atoms for each substance: a) 4g of hydrogen (H): 4 moles of hydrogen × (6.022 × 1023 atoms/mol) = 2.409 × 1024 atoms of hydrogen b) 4g of magnesium (Mg): 0.165 moles of magnesium × (6.022 × 1023 atoms/mol) = 9.923 × 1022 atoms of magnesium c) 71g of chlorine (Cl): 2 moles of chlorine × (6.022 × 1023 atoms/mol) = 1.204 × 1024 atoms of chlorine d) 127g of iodine (I): 1 mole of iodine × (6.022 × 1023 atoms/mol) = 6.022 × 1023 atoms of iodine
This question appeared on the ETEA MDCAT 2008 paper, which you can sit online with every answer explained.
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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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