Chemistry Problem

Question

How many milliliters of ammonium sulfate solution having a concentration of 0.243 M are needed to react completely with 38.8 mL of 2.53 M sodium hydroxide solution?

Answer 1

Write the balanced equation for the reaction in question:

(NH₄)₂SO₄ + 2NaOH ==> 2NH₃ + Na₂SO₄ + 2H₂O

Next, figure out how many moles of NaOH you have:

0.0388 L x 2.53 moles/L = 0.09816 moles NaOH

Next, using the balanced equation, calculate moles of (NH₄)2SO₄ needed to react with 0.09816 moles NaOH:

0.09816 moles NaOH x 1 mole (NH₄)₂SO₄/2 moles NaOH = 0.04908 moles  (NH₄)₂SO₄

Finally, knowing the molarity of the (NH₄)₂SO₄, calculate volume needed to obtain 0.04908 moles:

(0.243 moles/L)(x L) = 0.04908 moles and x = 0.20198 L = 201.98 ml = 202 ml (to 3 significan figures)

Make sense?