what is the solution’s concentration in g/L?

Question

If a student dissolves 5.082 g of NiCl2 * 6H2O in water in a 250.0 ml flask,

what is the solution’s concentration in g/L? (show all work)  convert mL to L ml to L divide by 1000 250/1000
5.082g/,25L = 20.33 g/L

 

what is the solution’s concentration in mol/L? (show all work)

5.082g X (1 mole/ 237.7(molar mass) = .021 mole     .021/.25=.084 mol/L
 

5 . If that student then removed 5.00ml of that solution and diluted it to 50.00 ml, what would the new solution’s concentration be in g/L? (hint: calculate the grams of solute in the 10.00 ml that were removed and divide it by the new volume in liters)


Taking out 5 mL. Have to find out how many grams are each mL. Convert g/L to g/ml 20.33/1000 = .02033 g/mL

.02033 X 5.00 mL = 0.1016 g/mL


now convert mL to L by dividing by 1000 0.1016/1000 = .0001016 g/L

new solution is 50 mL convert to liters 50/1000 = .05L

0.0001016 g/L/
.05 = .002032 g/L

Answer 1

Good job.  You have the concentration setup correctly for both g/Land mol/L.   Check your significant figures, each number given has 4 sig fig.  Answers should be written to 4 significant figures.

20.33g/ L

0.02138 mol/L

 

When changing volume of solution you can use the dilution equation for all concentration units and volume units.

 

 1.  C1V1 =C2V2

 2.  C1 = 20.33 g/L.   V1 = 5 mL. 

                                        5mL (1 L/1000mL) = 0.005 L

 3.  C2 = ?                 V2 = 50 mL  = 0.050 L

 4.  20.33 g/L* 0.005 L = C2 * 0.050 L

       0.10165 g = C2 * 0.050 L

       2.033 g/L