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a student decides to find the molar enthalpy for the reaction between phosphoric acid and calcium hydroxide. they have a 0.250 m solution of ca(oh)2, which they will use; they can only find a 2 m stock solution of h3po4. if they want 236 ml of a 0.22 m solution of h3po4, how many ml of the stock solution should they use to prepare their solution by diluting the stock?

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The triprotic acid phosphoric acid, also called orthophosphoric acid, is present as a viscous liquid. 74.3 mls H3PO4 needed to prepare their solution by diluting the stock.

What is phosphoric acid and calcium hydroxide?

  • The triprotic acid phosphoric acid, also called orthophosphoric acid, is present as a viscous liquid. Both humans and laboratory animals' skin, eyes, and other mucous membranes are irritated or damaged by it. The possibility for irritation in its salts, however, is substantially lower.
  • An inorganic solid with the chemical formula H3PO4, phosphoric acid is an odorless, colorless substance that contains phosphorus. It is frequently found as an 85% aqueous solution, which is a syrupy liquid that is colorless, odorless, and non-volatile.
  • Slaked lime, often known as calcium hydroxide, is an inorganic substance having the chemical formula Ca(OH)2. When water is combined with quicklime (calcium oxide), a colorless crystal or white powder is created.

First part:

Use V1M1 = V2M2 for such a dilution problem.

V1 = initial volume = ?

M1 = initial molarity = 2.1 M

V2 = final volume = 285 ml

M2 = final molarity = 0.31 M

(V1)(2.1)( = (285)(0.31)

V1 = 40.7 mls of 2.1 M H3PO4 are needed

Second part:

Utilising 0.28 M H3PO4, find mls needed to react with 125 ml of 0.250 M Ca(OH)2.

The balanced equation for this reaction is:  3Ca(OH)2 (aq) + 2H3PO4 (aq) ---> Ca3(PO4)2 (s) + 6H2O (l)

First we'll discover the moles of Ca(OH)2 present:

125 ml x 1 L/1000 ml x 0.250 mol/L = 0.03125 mols Ca(OH)2 present

From the balanced equation, we now find moles of H3PO4 needed:

0.03125 mols Ca(OH)2 x 2 mols H3PO4 / 3 mols Ca(OH)2 = 0.0208 mols H3PO4 needed

Finally, we find volume (mls) of H3PO4 needed:

0.0208 mols H3PO4 x 1 L / 0.28 mols = 0.0743 L x 1000 ml/L = 74.3 mls H3PO4 needed.

To learn more about phosphoric acid refer  to:

https://brainly.com/question/14812997

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