1. A solution of Na2SO4 containing 98.0 g of the salt and 850. mL of water was prepared at 25 °C. What is the mass percent of Na2SO4 in this solution?
Density of water at 25 °C: 1.00 g mL–1
2. A concentrated aqueous solution of sulfuric acid (H2SO4) was diluted and the concentration determined by titration with aqueous NaOH. 12.32 mL of 0.294 mol L–1 NaOH solution was required to neutralise a 20.00 mL aliquot of the diluted sulfuric acid solution. The equation for the titration reaction is as follows.
H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)
a) Calculate the number of moles of NaOH present in the 12.32 mL titre.
b) Use the stoichiometry of the titration reaction to determine the moles of H2SO4 present in the 20.00 mL sample.
c) What is the concentration (molarity) of the diluted H2SO4 solution?
3. The decomposition of solid KClO3 produces oxygen gas according to the equation below. 2KClO3(s) → 2KCl(s) + 3O2(g)
a) How many litres of oxygen form from complete decomposition of 294 g of KClO3 (molar mass 122.55 g mol–1) at 755 mm Hg and 305 K?
b) What was the percentage yield of this reaction if 51.7 L of O2 gas were produced?
4.Aerosol cans that contain residual propellant can rupture when heated due to the rapid increase in gas pressure within the rigid container. Explain the response of the gas to heating in terms of the motion of the gas molecules.
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