Question

Calculate the mass, in grams, of Ag2CrO4 that will precipitate when 50.0mL of 0.20M AgNO3 solution is mixed with 40.0mL of 0.10M K2CrO4 solution. Assume that Ag2CrO4 is completely insoluble (its Ksp is ~ 0).

Answer 1

1.327 g Ag₂CrO₄

Step-by-step explanation:

The reaction that takes place is:

• 2AgNO₃(aq) + K₂CrO₄(aq) → Ag₂CrO₄(s) + 2KNO₃(aq)

First we need to identify the limiting reactant:

We have:

• 0.20 M * 50.0 mL = 10 mmol of AgNO₃

• 0.10 M * 40.0 mL = 4 mmol of K₂CrO₄

If 4 mmol of K₂CrO₄ were to react completely, it would require (4*2) 8 mmol of AgNO₃. There's more than 8 mmol of AgNO₃ so AgNO₃ is the excess reactant. That makes K₂CrO₄ the limiting reactant.

Now we calculate the mass of Ag₂CrO₄ formed, using the limiting reactant:

• 4 mmol K₂CrO₄ *
  `(1mmolAg_2CrO_4)/(1mmolK_2CrO_4) *(331.73mg)/(1mmolAg_2CrO_4)` = 1326.92 mg Ag₂CrO₄

• 1326.92 mg / 1000 = 1.327 g Ag₂CrO₄