How do you figure out the molarity of a solution if the only information you have is the volume?

Question

How to you calculate molarity if you don't know the mass? The only information I have is How many litres of each liquid I started with.

If I have 10 mL H2SO4 and 10.4 mL NaOH, does that make H2SO4 the solute? I wasn't sure because the volumes were so close together.

Answer 1

Your question is a bit vague, but I think I can help.

If you know the concentrations of both starting solutions, then you are doing a mixing problem.

Remember that molarity is moles/liter, so

(molarity 1 * volume 1) + (molarity 2 * volume 2) = total moles of solute.

Then you divide the total moles of solute by the total volume of the solution, and you have the molarity of the mixture. The final equation would be:

Final molarity = (M1*V1 + M2*V2)/(V1 + V2)

Example: You have 0.5 liters of 3M solution of X, and 0.5 liters of 1M solution of X. what is the molarity of the mixture?

(3M * 0.5l + 1M * 0.5l)/(0.5l + 0.5l) = (1.5 mole + 0.5 mole)/1.0 liter = 2 moles/liter = 2M solution

Try that and see if it doesn't help.

Answer 2

Mass can be calculated directly from molarity and volume. 1 liter of a 1 molar solution has 1 mole of something dissolved in it. If two solutions are mixed and each has a different molarity, one first calculates the total number of moles and then the total volume. The ratio is then the molarity of the mixture. Of course if the only thing known is the volume, molarity can be calculated if one knows what was dissolved. One calculates the molecular weight of this substance, and then weighs the unknown solution. Water weighs 1 kilogram per liter. Any extra weight is the weight of the thing dissolved. If the only thing known is the volume, an nothing else, it is impossible to calculate molarity.

Answer 3

If you know what the solute is you can multiply the density (g/mL) by its volume (mL). This will give you the mass if the solute in grams. Once you have that divide it by its molecular weight. That will give you the number of moles. Finally divide the moles by the volume of the solvent (L) to give the molarity.

g/mL x mL = g
g/(g/mol) = moles
moles / vol of solvent (L) = molarity

Do these calculations and you will have your answer. Hope this helps.

Answer 4

Molarity is moles of solute over Liters of solution. So, Im not sure what they gave you. If you have Liters and know what the solute is look it up on the periodic table and figure out the weight of the solute and convert it to moles then divide it by your Liters of solution. I don't know what else you could do?

Answer 5

i think i would give up all together and forget that bullshit and just say i would rather spend my time drinking a 40