Question #ac64e

1 Answer
Stefan V.
Dec 4, 2017

Here's what I got.

Explanation:

Interestingly enough, the name sodium phosphate is actually used to describe a family of salts that contain sodium cations and phosphate anions in various ratios.

My guess is that you are supposed to treat "sodium phosphate" as trisodium phosphate, "Na"_3"PO"_4.

The idea here is that a formula unit of sodium phosphate, "Na"_3"PO"_4, contains

  • three sodium cations, 3 xx "Na"^(+)
  • one phosphate anion, 1 xx "PO"_4^(3-)

This, of course, implies that 1 mole of sodium phosphate will contain 3 moles of sodium cations and 1 mole of phosphate anions.

In other words, you have

  • "no. of moles of Na"^(+) = 3 xx "no. of moles of Na"_3"PO"_4
  • "no. of moles of PO"_4^(3-) = "no. of moles of Na"_3"PO"_4

Since you know that your sample contains 0.500 moles of sodium phosphate, you can say that it contains 1.50 moles of sodium cations and 0.500 moles of phosphate anions.

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