Chemistry Problem: Neutralizing Phosphoric Acid

What is the process to neutralize phosphoric acid with a solution of ammonia? How much of a 0.250 M solution of ammonia is needed to completely neutralize 16.5 mL of 2.15 M phosphoric acid? To neutralize 16.5 mL of 2.15 M phosphoric acid, you would require 3 moles of ammonia for every mole of phosphoric acid. Based on this ratio, 47.3 mL of a 0.250 M solution of ammonia would be needed.

The Neutralization Process:

Neutralization is a chemical reaction in which an acid and a base react to form a salt and water. In the case of phosphoric acid (H3PO4) and ammonia (NH3), the reaction proceeds as follows:

H3PO4 + 3NH3 -> NH4PO4 + 2NH4+

This reaction is dependent on the fact that phosphoric acid is a polyprotic acid and can donate three hydrogen ions (H+) when it reacts with a base like ammonia.

Calculating the Amount of Ammonia Needed:

To determine the amount of ammonia solution required to neutralize the given amount of phosphoric acid, we must first convert the volume of phosphoric acid into moles using the formula moles = Molarity * volume.

For phosphoric acid: Moles = 16.5 mL * 2.15 M = 0.03548 mol

Since phosphoric acid requires 3 moles of ammonia to fully react, we then divide this value by three to find the moles of ammonia needed.

0.03548 mol / 3 = 0.01183 mol of NH3

Finally, to calculate the volume of the ammonia solution needed, we use the formula volume = moles / Molarity.

Volume = 0.01183 mol / 0.250 M = 0.0473 L or 47.3 mL

Therefore, 47.3 mL of a 0.250 M solution of ammonia is needed to completely neutralize 16.5 mL of 2.15 M phosphoric acid.
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