Answer
0.52 molal
Work Step by Step
Molality is defined as moles of solute per kilogram of solvent so in this case it would be moles of phenol per kilogram of ethanol.
We have 20.8g of phenol and 425g of ethanol. First we convert the grams of phenol to moles of phenol.
Phenol C6H5OH -
Carbon is 12g/mol, H is 1g/mol, O is 16g/mol
MW = 12*6 + 5*1 + 16 + 1 = 94g/mol
Then we have 20.8g * (1mol/94g) = 0.221 mole phenol
For the ethanol, we have 425g, which is 0.425kg.
Then we have 0.221 moles/0.425kg = 0.52 molal
