11) D: 3.60 M
You know that the concentration has to be in between 2.00 M and 4.00 M because that simply doesn't work you cant get a molarity of anything higher than 4.00 or anything lower than 2.00. That rules out B and C. And it says you have much more of the 4.00 M solution so you know the answer has to be closer to 4.00 than 2.00 which leaves us with D: 3.60 M.
12) E: 188.7 mL
Use the formula Molarity1 x Volume1 = Molarity2 x Volume2.
You know the original molarity, (M1) the original volume, (V1) and the final molarity (M2). To solve for V2 arrange the formula to:
V2 = (M1 x V1)/M2 Plug in the given values -> V2=(.275M x 230.0mL) / 1.53 M
The number your calculator spits out is the volume LEFT on the hotplate, but we want the volume that evaporated. To find that use simple subtraction.
V(Evaporated) = V1-V2 ----> 188.7 mL