Question

Calculate the molarity M (moles of solute/liter of solution) of each of the following queous solution. The units of molarity are M, so that is the appropriate unit to use. (i.e. M=mol/L)

a. 3.75mol CaCl2 in 1.25L of solution

b. 0.001750 mol Li2Co3 in 25.0mL solution

c. 23.25ml glycerol C3H8O3 (d=1.265g/mL) in 250.0mL of solution

d. 55.0ml 2-propanol, CH3CHOHCH3 (d=0.786g/ml) in 250ml of solution

e. How many grams of C6H12O6 are there in 10.0ml of 4.25M C6H12O6 solution?

f. How many grams of CuS04.5H2O are there in 3.00L of a 0.275M solution? (in this problem the calculated molecular weight must include the pentahydrate!)

Answer 1

a. Molarity(M) = (w/Mwt)*(1/V in L)

w/Mwt = n = no of moles of solute = 3.75 mol

V = vol.of solution = 1.25 L

Molarity(M) = 3.75*(1/1.25) = 3 M

b.
Molarity(M) = (w/Mwt)*(1000/V in mL)

w/Mwt = n = no of moles of solute = 0.00175 mol

V = vol.of solution = 25 mL

Molarity(M) = 0.00175*(1000/25) = 0.07 M

c.

Molarity(M) = (w/Mwt)*(1000/V in mL)

w = weight of solute = 23.25*1.265 = 29.41 g

Mwt = molarmass of glycerol = 92.1 g/mol

V = vol.of solution = 250 mL

Molarity(M) = (29.41/92.1)*(1000/250)

             = 1.277 M

d.

Molarity(M) = (w/Mwt)*(1000/V in mL)

w = weight of solute = 55.0*0.786 = 43.23 g

Mwt = molarmass of 2-propanol = 60.1 g/mol

V = vol.of solution = 250 mL

Molarity(M) = (43.23/60.1)*(1000/250)

             = 2.9 M