If 45.5 mL of 0.150 M sodium sulfate solution reacts completely with aqueous barium nitrate, what is the mass of BaSO4 (233.40 g/mol) precipitate? Ba(NO3)2(aq)+Na2SO4(aq)BaSO4(s)+2NaNO3(aq)?

1 Answer
Oct 1, 2016

1.59g (3 s.f.)

Explanation:

In this reaction, every 1 mole of Na2SO4 produces 1 mole of BaSO4, as shown by the mole ratio in the equation. As the question states that all the Na2SO4 solution reacts, we can assume that Ba(NO3)2 is in excess as it allows for all the Na2SO4 to react. This means that the reaction is dependent on the moles of Na2SO4.

  1. Calculate the moles of Na2SO4
    n(Na2SO4) = 0.0455L x 0.150molL = 0.006825 mol
    Notice that the L units cancel out, leaving only moles; this is basic conversion
  2. Use the mole ratio of Na2SO4 to BaSO4 to find the moles of BaSO4. We established at the beginning that for every 1 mole of Na2SO4 that reacts, 1 mole of BaSO4 is produced. This means that the number of moles of Na2SO4 that we have will be identical to the number of moles of BaSO4 produced.
    n(BaSO4) = n(Na2SO4) = 0.006825 mol
  3. Use the molar mass of BaSO4 and the moles of BaSO4 to calculate the mass of BaSO4 produced
    molar mass: 137.3 + 32.07 + 4(16) = 233.37g/mol
    mass produced: 0.006825 mol x 233.37gmol = 1.59g (3 s.f.)