Question

If you mix 40.0 ml of a 0.200 m solution of k2cro4 with an aqueous solution of agno3, what mass of solid forms? (hint: most chromates are insoluble.)

Answer 1

The mass of solid formed is 2.654 g

calculation

step 1: write the balanced molecular equation

=2AgNO3(aq) + k2CrO4(aq)→ Ag2CrO4(s) + 2 KNO3(aq)

step 2: calculate the moles of K2CrO4

moles = molarity x volume in liters

molarity = 0.200 M = 0.200 mol/L

volume = 40 .0 ml in liters = 40/1000 = 0.04 liters

moles is = 0.200 mol/l x0.04 L =0.008 moles

Step 3: use the mole ratio to determine the moles of solid formed( Ag2CrO4)

K2CrO4 :Ag2CrO4 is 1:1 therefore the moles of Ag2CrO4 is also

0.008 moles

step 4: calculate the mass of Ag2CrO4

mass = moles x molar mass

from periodic table the molar mass of Ag2Cro4

=(107.87 x2) + 52 +(16 x4) =331.74 g/mol

mass = 0.008 moles x 331.74 = 2.654 g