Jesse E. answered • 07/28/19

Masters in Chemistry specializing in preparing for ACT Science.

By definition, molality is the number of moles of soluter per kg of solvent. (*It is very easy for students to read this problem and think molarity is needed. So be careful when reading problems.*)

For this problem, we need to convert maleic acid to moles by calculating its formula weight.

4 x C = 4 x (12 g/mol) = 48 grams/mole l

4 x O = 4 x (16 g/mol) = 64 grams/mole

4 x H = 4 x (1.0 g/mol) = 4 grams/mole

Adding these up we get the formula weight of maleic acid which 116 grams/mole.

Now we calculate moles:

30 (1 mol/116 grams) = 0.26 moles

For the molality, we divide the number of moles by the amount of solvent, which is 600 g, which is also 0.6 kg.

0.26 moles/0.6 kg = 0.43 moles/kg.

This solution's molality is 0.43 moles/kg