Acetonitrile, CH3CN, is a polar organic solvent that dissolves many solutes, including many salts. The density of a 1.80 M acetonitrile solution of LiBr is 0.826 g/mL. Calculate the concentration of the solution in units of (a) molality; (b) mole fraction of LiBr; (c) mass percentage of CH3CN.

(a)

(b)

(c)

Explanation:

Hello,

In this case, given the molality in mol/L, we can compute the required units of concentration assuming a 1-L solution of acetonitrile and lithium bromide that has 1.80 moles of lithium bromide:

(a) For the molality, we first compute the grams of lithium bromide in 1.80 moles by using its molar mass:

Next, we compute the mass of the solution:

Then, the mass of the solvent (acetonitrile) in kg:

Finally, the molality:

(b) For the mole fraction, we first compute the moles of solvent (acetonitrile):

Then, the mole fraction of lithium bromide:

(c) Finally, the mass percentage with the previously computed masses:

Regards.

po-215 i got it right on the quiz