1. _idk_
2. For this question, you have M=2 and 2.5 liters of solution.
So we need to find how many noles of Na2SO4 are needed.
Let's set up our fraction:
2=(moles Na2SO4)/2.5
Multiplying both sides by 2.5, we get that we need 2*2.5=5 moles of Na2SO4.
Now that we have the needed quantity of moles, we need to convert it to grams. Na=23, S=32, and O=16, so the molar mass of Na2SO4 is 23*2+32+16*4=142 grams.
Let's set up a multiplication bar:
(5 moles Na2SO4)(142g/[1 mol NaSO4])
The (moles Na2SO4) unit cancels out, and we are left with 5*142=710g Na2SO4 needed.
This is answer [D].
3.(mass solute/mass soln) = 0.06
4. mol of solute = 8.0 g x (1 mol / 24.0 g ) = 0.333 mol
molality = 0.333 mol / 0.50 kg = 0.67 molal
D) is the correct answer.
5. _idk_
