What Steps Solve a Complex Molarity Problem?

[pasido]

Homework Statement

http://i.imgur.com/Rz0qB.png

Homework Equations

The answer is B, but I would like to know how to find the answer.
Molarity = moles * volume

The Attempt at a Solution

Yep, I tried for 15+ minutes and couldn't get the darn units to cancel out. A worked out solution would be very helpful.

 

[sjb-2812]

Homework Statement

http://i.imgur.com/Rz0qB.png

Homework Equations

The answer is B, but I would like to know how to find the answer.
Molarity = moles * volume

The Attempt at a Solution

Yep, I tried for 15+ minutes and couldn't get the darn units to cancel out. A worked out solution would be very helpful.

Is there a reason you have provided an image, rather than text?

How many moles of Na+ do you need?

 

[symbolipoint]

The relevant equation, "Molarity = moles * volume", is wrong.

 

[ARlTHMOMANIA]

Molarity = mole per liter or mol/L

Determine the ratio of Na+ in Na3PO4 by observing the formulas (*Hint 1/3 or 3/1). Multiply this by your Molar concentration of Na+ given in the problem.

Next, set up a ratio of:

[Na*(1/3 or 3/1) (M)] / Na3PO4 (M)

or

Na3PO4 (M) / [Na*(1/3 or 3/1) (M)]

(reason whether the answer should be greater than 1 or less than 1 to determine which ratio to use).

Finally multiply this by the volume you're trying to prepare.