Avogadro's number Knowledge-Based Practice

Questions

1. 1.

   Which of the following pure substance samples contains the greatest total number of molecules? (Molar masses: $\text{CH}_4 = 16.04\text{ g/mol}$, $\text{O}_2 = 32.00\text{ g/mol}$, $\text{CO}_2 = 44.01\text{ g/mol}$, $\text{SO}_2 = 64.07\text{ g/mol}$)

   • A) $10.0\text{ g of }\text{CO}_2$
   • B) $10.0\text{ g of }\text{O}_2$
   • C) $10.0\text{ g of }\text{CH}_4$
   • D) $10.0\text{ g of }\text{SO}_2$
2. 2.

   What is the total number of ions present in a 0.200 mol sample of pure solid aluminum oxide, $\text{Al}_2\text{O}_3$? (Avogadro's constant, $N_{\text{A}} = 6.022 \times 10^{23}\text{ mol}^{-1}$)

   • A) $1.20 \times 10^{23}$
   • B) $6.02 \times 10^{23}$
   • C) $2.41 \times 10^{23}$
   • D) $3.61 \times 10^{23}$
3. 3.

   What is the mass, in grams, of a single molecule of nitrogen gas, $\text{N}_2$? (Molar mass of $\text{N}_2 = 28.02\text{ g/mol}$; Avogadro's constant, $N_A = 6.022 \times 10^{23}\text{ mol}^{-1}$)

   • A) $1.69 \times 10^{25}\text{ g}$
   • B) $2.33 \times 10^{-23}\text{ g}$
   • C) $4.65 \times 10^{-23}\text{ g}$
   • D) $2.15 \times 10^{22}\text{ g}$
4. 4.

   A sample of pure argon gas contains $1.806 \times 10^{24}$ atoms. How many moles of argon atoms are present in this sample?

   • A) 0.300 mol
   • B) 1.50 mol
   • C) 3.00 mol
   • D) 6.00 mol
5. 5.

   How many individual oxygen atoms are contained in a 0.50 mol sample of gaseous carbon dioxide ($\text{CO}_2$)?

   • A) $1.51 \times 10^{23}$
   • B) $3.01 \times 10^{23}$
   • C) $1.20 \times 10^{24}$
   • D) $6.02 \times 10^{23}$

Answers and step-by-step solutions appear after you finish the test.