What is the concentration of a phosphoric acid solution of a 25.00 mL sample of the acid requires 42.24 mL of 0.135 M NaOH for neutralization?

Question

Quizplus · Accepted Answer

The balanced chemical equation for the reaction between phosphoric acid (H3PO4) and sodium hydroxide (NaOH) is:

H3PO4 + 3 NaOH → Na3PO4 + 3 H2O

According to the equation, 1 mole of H3PO4 reacts with 3 moles of NaOH. Therefore, the number of moles of NaOH used in the titration is:

moles NaOH = concentration x volume = 0.135 M x 42.24 mL = 0.0057296 mol

Since 1 mole of NaOH reacts with 1 mole of H3PO4, the number of moles of H3PO4 in the 25.00 mL sample is also 0.0057296 mol. This corresponds to a concentration of:

concentration of H3PO4 = moles/volume = 0.0057296 mol/0.02500 L = 0.0760 M

Therefore, the answer is C.

What Is the Concentration of a Phosphoric Acid Solution of a 25.00