(0.8 mol/L) (1.5 L) = x / 56.1 g/mol

solve for x

question 2:

0.0036 g / 240 g = x / 1,000,000 g

x = 15 ppm

I have some discussion about ppm here:

http://www.chemteam.info/Solutions/ppm1.html

BTW, the above assumes the density of the solution is 1 g/mL. the 0.0036 g / 240 g is 3.6 mg per 240 mL of solution

question 3:

34.2 divided by (34.2 + 60.8) = 36% w/w

View the original article here