Avogadro's number Transitional Reasoning Download PDF

Questions

1. 1.

   A quality-control chemist prepares a standardized electrolyte solution by completely dissolving $0.050\text{ mol}$ of solid iron(III) sulfate, $\text{Fe}_2(\text{SO}_4)_3$, in deionized water. Complete dissociation yields aqueous iron(III) cations and sulfate anions according to the stoichiometry of the formula unit. Taking Avogadro's number as $N_A = 6.02 \times 10^{23}\text{ mol}^{-1}$, which pair of values represents the total number of dissolved ions and the total number of oxygen atoms originating from the solute?

   • A) $3.01 \times 10^{22}$ total ions and $1.20 \times 10^{23}$ oxygen atoms
   • B) $1.51 \times 10^{23}$ total ions and $1.20 \times 10^{23}$ oxygen atoms
   • C) $1.51 \times 10^{23}$ total ions and $3.61 \times 10^{23}$ oxygen atoms
   • D) $3.01 \times 10^{23}$ total ions and $5.12 \times 10^{23}$ oxygen atoms
2. 2.

   An ultra-sensitive mass spectrometer detects an individual molecule of an unbranched alkane hydrocarbon with the general formula $\text{C}_n\text{H}_{2n+2}$ having an absolute mass of $7.31 \times 10^{-23}\text{ g}$. Using Avogadro's number ($N_{\text{A}} = 6.02 \times 10^{23}\text{ mol}^{-1}$) and the atomic molar masses $\text{C} = 12.0\text{ g/mol}$ and $\text{H} = 1.0\text{ g/mol}$, which values correctly identify the molar mass and molecular formula of this alkane?

   • A) 16 g/mol and $\text{CH}_4$
   • B) 30 g/mol and $\text{C}_2\text{H}_6$
   • C) 58 g/mol and $\text{C}_4\text{H}_{10}$
   • D) 44 g/mol and $\text{C}_3\text{H}_8$
3. 3.

   A semiconductor laboratory deposits a high-purity monatomic metallic film onto a microchip component. A surface analysis instrument determines that the deposited layer contains exactly $3.01 \times 10^{20}$ atoms of the metal and has a total mass of $0.0540\text{ g}$. Taking Avogadro's number as $N_A = 6.02 \times 10^{23}\text{ mol}^{-1}$, what are the molar amount and the molar mass of the deposited metal?

   • A) $2.00 \times 10^{-3}\text{ mol}$ and $27.0\text{ g/mol}$
   • B) $5.00 \times 10^{-3}\text{ mol}$ and $10.8\text{ g/mol}$
   • C) $1.00 \times 10^{-3}\text{ mol}$ and $54.0\text{ g/mol}$
   • D) $5.00 \times 10^{-4}\text{ mol}$ and $108\text{ g/mol}$
4. 4.

   An environmental monitoring device in a facility records a release of dinitrogen monoxide ($\text{N}_2\text{O}$) gas that contains exactly $6.02 \times 10^{22}$ nitrogen atoms. To assess the emission, the operator must determine the molar amount of the compound emitted and the total number of $\text{N}_2\text{O}$ molecules present. Taking Avogadro's number as $N_A = 6.02 \times 10^{23}\ \text{mol}^{-1}$, which pair of values accurately represents the molar amount and the molecule count of this gas sample?

   • A) $0.10\ \text{mol}$ of $\text{N}_2\text{O}$ and $6.02 \times 10^{22}$ molecules
   • B) $0.05\ \text{mol}$ of $\text{N}_2\text{O}$ and $3.01 \times 10^{22}$ molecules
   • C) $0.20\ \text{mol}$ of $\text{N}_2\text{O}$ and $1.204 \times 10^{23}$ molecules
   • D) $0.05\ \text{mol}$ of $\text{N}_2\text{O}$ and $9.03 \times 10^{22}$ molecules
5. 5.

   A researcher prepares two sealed containers: Container X contains 0.60 mol of argon gas (Ar), and Container Y contains 0.20 mol of sulfur trioxide gas ($\text{SO}_3$). If Avogadro's number is represented by $N_A$, which statement correctly evaluates the particle and atom counts in the two containers?

   • A) Container X contains three times as many gas particles as Container Y, but Container Y contains a greater total number of atoms ($0.80 N_A$) than Container X ($0.60 N_A$).
   • B) Container X contains three times as many gas particles as Container Y, and Container X also contains a greater total number of atoms ($1.80 N_A$) than Container Y ($0.80 N_A$).
   • C) Both containers contain an equal total number of atoms because 0.60 mol of monoatomic argon equals the total atom count in 0.20 mol of sulfur trioxide.
   • D) Container X contains fewer gas particles than Container Y, but Container X contains a greater total number of atoms than Container Y.