mixing solutions?

Question

if you mix 20.0 mL of a 3.00 M sugar soltuion with 30.0mL of a 5.00 M sugar solution you will end up with a sugar solution of what?

Answer 1

Assuming that the sugar in both solutions is the same compound, your final volume will be : 30+20 = 50 ml.

The easiest way is to calculate the n. of moles in each solution and divide by the volume:

from the first 20ml of the 3M solution you obtain 60mmoles
[because you have 3mol/l or 3mM/ml ==> 60mmoles in 20ml]

from the second 30ml, with an analogous reasoning, you obtain 150mmoles.

Tot. mmoles: 210 in 50ml ===> Conc of 4.2mmol/ml or 4.2M

You can also apply the general rule whereby:

Ci*Vi = Cf*Vf.

Answer 2

Calculate the number of moles in each original sugar solution from the molarities and their volumes (in Liters). Then, add the number of moles of sugar together. Finally divide the total moles of sugar by the total volume (in Liters) of the final solution.

Answer 3

1. find the number of moles in each solution :
A = 20/1000 *3 = 0.06mols
B= 30/1000 *5 = 0.15mols
2. add the n. of moles = 0.21 mols
3. divide the number of moles by the volume of the final solution (i.e. 20ml+30ml = 50ml)
M(final) = 0.21/50 *1000 = 4.2M

hope it helps

Answer 4

Total volume =50 mL
Mole sugar first solution =0.06 =(3)(20)/1000

..."......." ......second solution = 0.15 = (5)(30)/1000

Total mole = 0.21

Total volume = 50 mL=0.050 L

M =0.21/0.05=4.2 M