Question

You have 75.0 mL of a 2.50 M solution of Na2CrO4(aq). You also have 125 mL of a 1.72 M solution of AgNO3(aq). Calculate the concentration of Ag+ after the two solutions are mixed together.

Answer 1

The thing to realize here is that when you pour these two solutions together, that all concentrations will drop (as they are diluted). So you have to fine the new molarity for each one.

First find initial moles of each ion.

Moles= Molarity times volume in LITERS.

Moles Na= = 2.5 molar Na2CrO4 times 2 moles Na+/mole times .075 Liters = .375 moles Na+

Moles CrO4= = 2.5 molar Na2CrO4 times one mole CrO4=/mole times .075 liters=.187 Moles CrO4=

Moles Ag+ = 2.5 molar AgNO3 times one mole Ag+/mole times .125 Liters= .31 moles Ag+

Moles NO3- 2.5 molar AgNO3 times one mole NO3-/mole times .125 liters = .31 moles NO3-

Now to get Molarity of each ion.

Molarity each ion = moles of ion over total volume of .200 Liters (I added 75ml+125ml)= 200ml or .200 liter.

So just divide moles of each ion above by .200 Liters and you will have Molarity of each ion in this solution