Question #33682

1 Answer
Ernest Z.
May 14, 2017

Add 3.0 L of concentrated phosphoric acid to enough water to make 15.0 L of solution.

Explanation:

Yes, "Molarity" = "moles"/"litres", so

"3.0 mol/L" = x/"15.0 L"

x = "3.0 mol"//color(red)(cancel(color(black)("L"))) × 15.0 color(red)(cancel(color(black)("L"))) = "45 mol"

So, you would add 45 mol of phosphoric acid to enough water to get 15.0 L of solution.

From where do you get the 45 mol of phosphoric acid?

You get it from concentrated phosphoric acid, which has a concentration of 14.8 mol/L.

Again, you use the formula, "Molarity" = "moles"/"litres".

"Molarity" = "moles"/x

"14.8 mol/L" = "45 mol"/x

x= (45 color(red)(cancel(color(black)("mol"))))/(14.8 color(red)(cancel(color(black)("mol")))//"L") = "3.0 L"

So, you would carefully add 3.0 L of concentrated phosphoric acid with stirring to about 11 L of water and then add more water until you have 15.0 L of solution.

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