Molar mass Knowledge-Based Practice

Questions

1. 1.

   Which of the following 25.0 g samples contains the greatest amount of substance in moles? (Molar masses: $\text{CO}_2 = 44.01\text{ g/mol}$, $\text{O}_2 = 32.00\text{ g/mol}$, $\text{H}_2\text{O} = 18.02\text{ g/mol}$, $\text{CH}_4 = 16.04\text{ g/mol}$)

   • A) 25.0 g of $\text{CO}_2$
   • B) 25.0 g of $\text{O}_2$
   • C) 25.0 g of $\text{H}_2\text{O}$
   • D) 25.0 g of $\text{CH}_4$
2. 2.

   Given that the molar mass of gold is 196.97 g/mol and Avogadro's constant is $6.022 \times 10^{23}\text{ mol}^{-1}$, what is the average mass of a single gold atom in grams?

   • A) $1.186 \times 10^{26}\text{ g}$
   • B) $3.057 \times 10^{21}\text{ g}$
   • C) $3.271 \times 10^{-22}\text{ g}$
   • D) $3.271 \times 10^{-24}\text{ g}$
3. 3.

   An element $X$ forms an oxide with the formula $X_2\text{O}_3$. If the molar mass of this oxide is 101.96 g/mol, what is the molar mass of element $X$? (Molar mass of $\text{O} = 16.00\text{ g/mol}$)

   • A) 53.96 g/mol
   • B) 26.98 g/mol
   • C) 42.98 g/mol
   • D) 85.96 g/mol
4. 4.

   A 0.350 mol sample of an unknown pure gas has a mass of 15.4 g. What is the molar mass of this gas?

   • A) 5.39 g/mol
   • B) 44.0 g/mol
   • C) 22.7 g/mol
   • D) 88.0 g/mol
5. 5.

   What is the molar mass of calcium phosphate, $\text{Ca}_3(\text{PO}_4)_2$, given the atomic masses of calcium (40.08 g/mol), phosphorus (30.97 g/mol), and oxygen (16.00 g/mol)?

   • A) 215.21 g/mol
   • B) 246.18 g/mol
   • C) 310.18 g/mol
   • D) 270.10 g/mol

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