Question

PLEASE HELP! ONLY SERIOUS ANSWERS! I APPRECIATE ANYTHING!! 30PTS!!! 1.The volume of 3.50M HCl needed to make 275mL of 2.90M HCl is a. 153mL b. 228mL c. 255mL d. 332mL 2. What mass of Na2SO4 is needed to make 1.8 L of 3.0 M solution? (Na = 23 g; S = 32 g; O = 16 g a. 142g b. 334g c. 767g d. 1,534g 3. If the percent (mass/mass) for a solute is 6% and the mass of the solution is 300 g, what is the mass of solute in solution? a. 18g b. 36g c. 72g d. 180g 4. What is the molality of a solution containing 9.5 grams of solute in .75 kg of solvent? ( molar mass of solute is 33.2 g/mole) a. 12.7m b. 5.75m c. 0.382m d. 0.0789m 5. What is the freezing point of a solution of 0.650 mol sucrose in 750.0mL of water ? (Kf of water = 1.86 deg C/m) a. 1.61 deg c b. 0.00 deg c c. -1.61 deg c d. it would not freeze

Answer 1

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_