Atomic Mass & The Mole
What device is used to determine atomic masses with high precision?
Mass spectrometer
Convert 320.0 g of Cu to moles. (Cu = 63.55 g/mol)
5.04 mol Cu
Define percent composition
The percent by mass of each element in a compound.
What is the empirical formula of hydrogen peroxide (H₂O₂
Balance:
C₃H₈ + O₂ → CO₂ + H₂O
C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O
How many atoms are in 1.00 mol of any element?
6.022 x 1023
What volume does 0.16 mol of Fe occupy? (Density = 7.874 g/mL)
1.1 mL
What is the mass percent of Na in NaClO₂? (MM = 90.44 g/mol)
25.4% Na
Vitamin C has empirical formula C₃H₄O₃ and molar mass 175 g/mol. What is its molecular formula?
C₆H₈O₆
Balance
Al + Fe₂O₃ → Al₂O₃ + Fe
Al + Fe₂O₃ → Al₂O₃ + 2 Fe
Copper has two isotopes: Cu‑63 (69.09%) and Cu‑65 (30.91%). What is its average atomic mass?
63.55 amu
How many grams are in 3.5 mol of SF₆? (MM = 146.05 g/mol)
511 g
What percent of KMnO₄ is oxygen? (MM = 158.03 g/mol)
40% O
Glucose has empirical formula CH₂O and molar mass 180.06 g/mol. What is its molecular formula?
C₆H₁₂O₆
If 1 Xe atom has a mass of 131.29 amu, what is the mass of 1 mol of Xe?
131.29 g
What is the molar mass of Ca₃(PO₄)₂?
310.17g/mol
A compound is 52.1% C, 13.1% H, 34.7% O. What is its empirical formula?
C2H6O
A compound is 64.82% C, 13.59% H, 21.59% O. What is its empirical formula?
C10H30O4
How many atoms are in 1.000 g of boron (10.81 g/mol)
5.57 x 1022
How many moles of Ca₃(PO₄)₂ are in 10.0 g?
.0322 mol
A compound is 26.6% K, 35.4% Cr, 38.0% O. What is its empirical formula?
K2Cr2O7
What is the integer multiple relating molecular and empirical formulas?
molar mass ÷ empirical mass