Question #5650b

1 Answer
Sep 17, 2015

Sodium forms three anhydrous monophosphates with the three phosphates.

Explanation:

Sodium and the phosphate anion can actually only form one compound, trisodium phosphate, Na3PO4.

The other two compounds you're probably referring to are actually formed with the dihydrogen phosphate, H2PO4, and hydrogen phosphate, HPO24, anions.

Moreover, sodium can form monophosphates and polyphosphates, in several anhydrous and hydrate forms, so I will assume that you're interested in the anhydrous monophosphates here.

  • monosodium phosphate

This compound is formed when one sodium cation, Na+, combines with one dihydrogen phosphate anion, H2PO4.

The salt dissociates completely in aqueous solution

NaH2PO4(aq]Na+(aq]+H2PO4(aq]

  • disodium phosphate

This compound is formed when two sodium cations combine with one hydrogen phosphate anion, HPO24.

Na2HPO4(aq]2Na+(aq]+HPO24(aq]

  • trisodium phosphate

This time, you have three sodium cations and one phosphate anion, PO34.

Na3PO4(aq]3Na+(aq]+PO34(aq]