AS 2

Practice Calculations for 91161
1. What is the mass of 0.275 mol of Na2CO3?
M(Na2CO3) = 106 gmol-1)
2. 12.2g of washing soda, Na2CO3 is dissolved in water to make exactly 1L of solution. Calculate the
concentration of Na2CO3 in molL-1.
3. How many moles of glucose are present in 16.0 mL of 0.320 molL-1 glucose solution?
M(glucose) = 180 g.mol-1
4. Oil of Wintergreen is the compound responsible for the smell in muscle liniments. Its formula is C 8O3H8.
What percentage of the compound is oxygen? M(C) = 12.0 g.mol-1, M(H) = 1.00 g.mol-1, M(O) = 16.0 g.mol-1
5. Stearic acid is an important fatty acid in animals. This molecule is 76.1% carbon, 11.2% oxygen, and 12.7%
a) Calculate the empirical formula of stearic acid.
b) If the molar mass of stearic acid is 284 gmol-1, calculate its molecular formula.
6. Quicklime (calcium oxide, CaO) is made by strongly heating limestone (calcium carbonate, CaCO3) according
to the equation below:
CaCO3 → CaO + CO2
Calculate the mass of quicklime that could be produced from 48.0 g of limestone.
M(CaCO3) = 100 g.mol-1, M(CaO) = 56 g.mol-1
7. 7.5g of magnesium (Mg) is completely dissolved in excess hydrochloric acid (HCl).
2HCl + Mg → MgCl2 + H2
Calculate the mass of magnesium chloride (MgCl2) that could be recovered from the resulting solution
M(MgCl2) = 95.3 g.mol-1, M(Mg) = 24.3 g.mol-1
8. 20 mL samples of diluted hydrochloric acid were titrated against 0.023 mo.lL-1 sodium hydroxide. The titres
of NaOH were 14.35 mL, 14.10mL, 14.10mL, 14.20mL. Calculate the concentration of HCl.
Balanced equation: NaOH + HCl → NaCl + H2O