Chemistry - Moles, Molar Mass, and Relative Atomic Mass

Flashcards covering key definitions, molar mass calculations, relative atomic mass formulas, and mole conversion concepts from the lecture notes.

Relative atomic mass

The weighted average mass of an atom of an element taking into account the mass of all isotopes and their relative abundance.

Average atomic mass formula ($M_{ave}$)

The formula used to calculate relative atomic mass: $M_{ave} = \frac{\sum (\% \text{ abundance} \times \text{Isotope mass})}{100}$.

Avogadro's number

The counting unit constant equal to $6.02 \times 10^{23}$, representing the number of items in one mole.

Mole

A unit abbreviated as mol that equals $6.02 \times 10^{23}$ particles, used to measure chemical amounts because individual atoms/molecules are too small to count directly.

Molar mass

The mass in grams of $1\,\text{mol}$ of a substance, with units expressed in $\text{g\,mol}^{-1}$.

Atom breakdown of $Ca(ClO_3)_2$

A compound formula containing $1$ atom of Calcium ($Ca$), $2$ atoms of Chlorine ($Cl$), and $6$ atoms of Oxygen ($O$).

Molar mass of $Ca(ClO_3)_2$

Calculated as $40.08\,\text{g}$ (Ca) + $2(35.45)\,\text{g}$ (Cl) + $6(16.00)\,\text{g}$ (O) = $206.98\,\text{g}$.

Atom breakdown of $Sn(SO_4)_2$

A compound formula containing $1$ atom of Tin ($Sn$), $2$ atoms of Sulfur ($S$), and $8$ atoms of Oxygen ($O$).

Molar mass of $Sn(SO_4)_2$

Calculated as $118.71\,\text{g}$ (Sn) + $64.12\,\text{g}$ (S) + $128\,\text{g}$ (O) = $310.83\,\text{g\,mol}^{-1}$, which rounds to $310.8\,\text{g\,mol}^{-1}$.

Gold mole conversion

Converting $7.25 \times 10^8\,\text{g Au}$ to moles using molar mass $196.97\,\text{g\,mol}^{-1}$ yields $3.68 \times 10^6\,\text{mol Au}$.

Neon relative atomic mass calculation

Calculated as $M_{ave} = \frac{(20 \times 90.48) + (21 \times 0.27) + (22 \times 9.25)}{100} = \frac{1809.6 + 5.67 + 203.5}{100} = 20.19\,\text{amu}$.

Lithium relative atomic mass calculation

Calculated as $M_{ave} = \frac{(6 \times 7.42) + (7 \times 92.58)}{100} = \frac{44.52 + 648.06}{100} = 6.9258$.