Magnesium Oxide Lab Activity
25
= 1 mark
Question: (see lab handout)
Predictions: molecular formula of magnesium mass % magnesium (%Mg)
mass % oxygen (%O)
Observations: Table 1: _______________________________
mass (g)
crucible + lid
26.467
crucible + lid + Mg
26.571
crucible + lid + MgO
26.597
1
Analysis:
1.a) mass of Mg
= 26.571g ­ 26.467g = 0.104 g of Mg
b) mass of magnesium oxide
= 26.597g ­ 26.467g = 0.130 g of Mg
c) mass of O = 0.130g ­ 0.104g = 0.026 g of Mg
d) percentage composition:
experimental mass % Mg = g of Mg x 100%
g of MgO
experimental mass % O =
= g of O x 100%
g of MgO
percentage composition is ______% Mg and _____% O
e) Find the Empirical Formula * Use the percent composition you calculated and assume 100g sample*
Element %
Mass (g) *
Molar mass
(g/mol)
Number Smallest Whole of moles number ratio (mol)
Mg O Experimental Empirical Formula ____________
2
2. a) Actual (Theoretical) Empirical Formula is MgO
Molar Mass Mg
Actual mass % Mg = 24.305 g/mol
Molar Mass MgO
= b) Percent Error = Experimental Mass %Mg ­ Actual Mass %Mgx100%
Actual Mass %Mg
3. The empirical formula needs to be rounded to a whole number because...
Conclusion
4. Empirical formula predicted _______________
Empirical formula obtained _______________
compare
3