Question

What is the final concentration of a mixture of 1.50 liters of 1.50 M H2S04 and 500 mL of water ? Why does the moles of water not effect the calculation? Why not use Mv (intial) =Mv(final) ?

Answer 1

             Initial                              Final

M1= 1.50M                          M2=

V1=1.50L                                V2= 500 +1500=2000m=2.0L

for dilution

M1V1= M2V2

1.5x1.5= M2x2.0

M2= 1.125M

Final concentration = 1.125M

In the initial concentration,

M1= number of moles of solute/volume in L.

i.e M1=n1/V1

n1= M1V1

for diluting the process,by adding the required quantity of water,but there is no chnage in the number of moles of solute., only change in the volume of solution,

M2= n1/V2

n1=M2V2

Hence n1=n1

M1V1=M2V2

Hence there is no effect of water in the dilution.