What is the molality of a solution in which 20.0 mL of ethanol is added to 80.0 mL of water (density 0.998 g/mL)? A 0.433 m
B 1.26 m
C. 2.95 m
D 3.43 m
E 4.30 m

Ineed ! i have no clue how to do this problem.

Find the mass, in grams, of 5.00*10^23 molecules of f2

For a research project, a student decided to test the effect of the lead(ii) ion (pb2+) on the ability of salmon eggs to hatch. this ion was obtainable from the water‐soluble salt, lead(ii) nitrate, which the student decided to make by the following reaction. pbo(s) + 2 hno3(aq) → pb(no3)2(aq) + h2o losses of product for various reasons were expected, and a yield of 86.0% was expected. in order to have 5.00 g of product at this yield, how many grams of pbo should be reacted? (assume that sufficient nitric acid, hno3, would be used.)