Ascientist wants to make a solution of tribasic sodium phosphate, na3po4, for a laboratory experiment. how many grams of na3po4 will be needed to produce 400. ml of a solution that has a concentration of na+ ions of 1.00 m ?
express your answer to three significant figures and include the appropriate units.

137g of Na3PO4

Explanation:

We sort of need to work backwards in this case. First figure out how many total Na+ ions there will be:

C = n/V

1 = n/0.4

n=2.5

The solution will contain 2.5 moles of Na+ ions. Now, notice that in Na3PO4 there are 3 Na atoms per molecule. That means if there are 2.5 moles of Na, there are 3 times LESS moles of Na3PO4.

2.5/3 = 0.833

Therefore 0.833 moles of Na3PO4 will be required. Now it's just a simple matter of converting to grams (using molar mass of Na3PO4):

n = m/MM

0.833 = m/164

m = 137

A total of 137g of Na3PO4 will be required.

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