Mole conversions (mass, particles, gas volume at STP) Transitional Reasoning Download PDF

Questions

1. 1.

   An analytical chemist collects a 10.0 g gaseous sample composed exclusively of neon (Ne) and argon (Ar) inside a rigid sampling cylinder. At standard temperature and pressure (STP), this entire gaseous mixture occupies a volume of 6.72 L. What is the mass of argon present in the sample, and how many individual neon atoms does the mixture contain? (Molar masses: $\text{Ne} = 20.0\text{ g/mol}$, $\text{Ar} = 40.0\text{ g/mol}$; Avogadro's number, $N_A = 6.02 \times 10^{23}\text{ atoms/mol}$; molar volume of an ideal gas at STP = $22.4\text{ L/mol}$)

   • A) 4.00 g of Ar and $1.20 \times 10^{23}$ Ne atoms
   • B) 6.00 g of Ar and $9.03 \times 10^{22}$ Ne atoms
   • C) 8.00 g of Ar and $6.02 \times 10^{22}$ Ne atoms
   • D) 2.00 g of Ar and $2.41 \times 10^{23}$ Ne atoms
2. 2.

   Two separate gas cylinders, X and Y, are maintained under standard temperature and pressure (STP). Cylinder X contains 4.48 L of ethane gas ($\text{C}_2\text{H}_6$), while Cylinder Y contains a sample of propane gas ($\text{C}_3\text{H}_8$) that has the exact same total number of hydrogen atoms as Cylinder X. Based on this information, what are the mass of the propane gas in Cylinder Y and the volume it occupies at STP? (Molar masses: $\text{C} = 12.0\text{ g/mol}$, $\text{H} = 1.0\text{ g/mol}$; molar volume of an ideal gas at STP = $22.4\text{ L/mol}$)

   • A) 8.80 g and 4.48 L
   • B) 6.60 g and 4.48 L
   • C) 8.80 g and 3.36 L
   • D) 6.60 g and 3.36 L
3. 3.

   A deep-sea research probe samples a pocket of pure methane gas ($\text{CH}_4$) from a hydrothermal vent. Laboratory mass spectrometry establishes that this specific gas sample contains a total of $9.03 \times 10^{23}$ atoms. What are the mass of this methane sample and the volume it would occupy at standard temperature and pressure (STP)? (Molar mass of $\text{CH}_4 = 16.0\text{ g/mol}$; Avogadro's constant, $N_A = 6.02 \times 10^{23}\text{ atoms/mol}$; molar volume of a gas at STP = $22.4\text{ L/mol}$)

   • A) Mass = 24.0 g and Volume = 33.6 L
   • B) Mass = 6.00 g and Volume = 8.40 L
   • C) Mass = 4.80 g and Volume = 6.72 L
   • D) Mass = 120 g and Volume = 168 L
4. 4.

   A leak-detection sensor in an industrial facility captures a 5.60 L sample of an unidentified pure elemental diatomic gas at standard temperature and pressure (STP). Laboratory analysis confirms that this exact sample has a mass of 7.00 g. Based on this information, which option correctly identifies the gas and gives the total number of individual atoms contained within the sample? (Molar volume of a gas at STP = 22.4 L/mol; Avogadro's constant, $N_A = 6.02 \times 10^{23}\text{ particles/mol}$; atomic masses: $\text{N} = 14.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, $\text{F} = 19.0\text{ g/mol}$)

   • A) $\text{O}_2$ gas with a total of $3.01 \times 10^{23}$ atoms
   • B) $\text{N}_2$ gas with a total of $3.01 \times 10^{23}$ atoms
   • C) $\text{N}_2$ gas with a total of $1.51 \times 10^{23}$ atoms
   • D) $\text{O}_2$ gas with a total of $1.51 \times 10^{23}$ atoms
5. 5.

   A rigid laboratory canister holds an 11.0 g sample of pure carbon dioxide gas (CO2, molar mass = 44.0 g/mol). To calibrate an environmental sensor, the entire gas sample is completely transferred into an expandable balloon at standard temperature and pressure (STP, 0 °C and 1.00 atm). Based on these conditions, what is the volume occupied by the balloon at STP and how many total oxygen atoms are present in the sample? (Let NA represent Avogadro's constant, and the molar volume of a gas at STP = 22.4 L/mol.)

   • A) 2.80 L and 0.25 NA oxygen atoms
   • B) 5.60 L and 0.25 NA oxygen atoms
   • C) 5.60 L and 0.50 NA oxygen atoms
   • D) 11.2 L and 0.50 NA oxygen atoms