Question

Make 50 mL of a 4M solution.

Answer 1

soo... anything else? anything you want to solve for?

Answer 2

no that's all the problem is asking me for.

Answer 3

use this formula for molarity:
As molar concentration = n/V (number of moles per volume of solution)
n = cV = 4M x 0.050 L = 0.2 moles of solute (makes sure volume is in litres to match the mol/L concentration unit)

So weight out an equivalent of 0.2 moles of solute (first convert moles to grams)
Then dissolve this amount in about 40ml to start (as it could displace a bit of volume when the solute dissolves). Then continue adding volume till the final solution is 50ml.

So in short if you need to make a a volume V of stock solution of concentration c:
1) Calculate number of moles of solute required using n = cV
2) Convert this to grams and weigh out the solute
3) Dissolve this thoroughly in solution with MilliQ water (or of sufficient grade), close to the volume.
4) Continue adding volume to solution till you reach the target volume.

Answer 4

i'm still kind of lost. I know the answer is 8 grams. I just don't know how to write it out.

Answer 5

What kind of solution is it? NaCl?

Answer 6

Since the answer is 8 grams, it would have to be a 40 g/mol element or compound.

Answer 7

For 0.2 mol to be 8 grams.

Answer 8

It said the solution was a "kool-aid solution"

Answer 9

Hm, that is really strange. Kool-aid is basically glucose, which has a molar mass of about 180 g/mol

Answer 10

Sorry, that should be sucrose, not glucose, which has a molar mass of about 342 g/mol.

Answer 11

yea but the it says the answer is 8 grams so im just confused

Answer 12

Yeah, I'm not getting that either. Not sure what to tell ya.