Answer
a. Mass of a Na atom = 3.818 x $10^{-23}$ g
b. Mass of an N atom =2.326 x $10^{-23}$ g
c. Mass of a C$H_{3}$Cl molecule = 8.383 x $10^{-23}$ g
d. Mass of a $Hg(NO_{3})_{2}$ formula unit = 5.392 x $10^{-22}$ g
Work Step by Step
Strategy: To calculate the mass of one atom, molecule, or formula unit, we should use:1- Molar mass, that is the mass of one mole of substance 2- relationship of mole and Avogadro's number .
a. Mass of Na atom. The atomic mass of Na is 22.989 amu, so the molar mass of Na is 22.989 g/mol. 1 mol Na has Avogadro's number atoms that is 6.02 x $10^{23}$.
Mass of a Na atom = $\frac{molar mass Na}{Avogadro's number}$
Mass of a Na atom = $\frac{22.989g}{6.02 \times 10^{23}}$
Mass of a Na atom = 3.818 x $10^{-23}$ g
b. Mass of N atom. The atomic mass of N is 14.006 amu, so the molar mass of Na is 14.006 g/mol. 1 mol N has Avogadro's number atoms that is 6.02 x $10^{23}$.
Mass of an N atom = $\frac{molar mass N}{Avogadro's number}$
Mass of an N atom = $\frac{14.006g}{6.02 \times10^{23}}$
Mass of an N atom =2.326 x $10^{-23}$ g
c. Mass of C$H_{3}$Cl molecule.
Molar mass of C$H_{3}$Cl = 12.01 + 3 x 1.007 + 35.45
Molar mass of C$H_{3}$Cl = 50.471 g/mol
1 mol C$H_{3}$Cl has Avogadro's number atoms that is 6.02 x $10^{23}$.
Mass of a C$H_{3}$Cl molecule = $\frac{molar mass_{CH_{3}Cl}}{Avogadro's number}$
Mass of a C$H_{3}$Cl molecule = $\frac{50.471 g}{6.02 \times10^{23}}$
Mass of a C$H_{3}$Cl molecule = 8.383 x $10^{-23}$ g
d. Mass of $Hg(NO_{3})_{2}$ formula unit.
Molar mass $Hg(NO_{3})_{2}$ = 1 AM Hg + 2 AM N + 6 AM O
Molar mass $Hg(NO_{3})_{2}$ = 1 X 200.59 + 2 x 14.0067 + 6 x 15.999
Molar mass $Hg(NO_{3})_{2}$ = 324.597 g
Mass of a $Hg(NO_{3})_{2}$ formula unit = $\frac{molar mass_{$Hg(NO_{3})_{2}$}}{Avogadro's number}$
Mass of a $Hg(NO_{3})_{2}$ formula unit = $\frac{324.597 g}{6.02 \times10^{23}}$
Mass of a $Hg(NO_{3})_{2}$ formula unit = 53.920 x $10^{-23}$ g
Mass of a $Hg(NO_{3})_{2}$ formula unit = 5.392 x $10^{-22}$ g