What is the molarity of a phosphoric acid solution if 32.3 mL of the phosphoric acid solution is titrated to the final equivalence point with 20.6 mL of 0.581 M sodium hydroxide acid solution?
H3PO4 + 3NaOH ==> Na3PO4 + 3H2O
mols NaOH = 0.0206L*0.581 M= ??
mols H3PO4 = 1/3*?? = xx.
M=mols/L = xx/0.0323 = answer.
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To find the molarity of the phosphoric acid solution, you need to use the stoichiometry of the balanced chemical equation and the volume and concentration of the sodium hydroxide solution used in the titration.
First, calculate the number of moles of sodium hydroxide (NaOH) used:
Number of moles of NaOH = Volume of NaOH solution (in liters) * Concentration of NaOH solution
Given:
Volume of NaOH solution = 20.6 mL = 0.0206 L
Concentration of NaOH solution = 0.581 M
Calculating:
Number of moles of NaOH = 0.0206 L * 0.581 M = 0.0119646 mol (rounded to 5 decimal places)
According to the balanced chemical equation, the stoichiometric ratio between NaOH and H3PO4 is 3:1. This means that for every 3 moles of NaOH, there's 1 mole of H3PO4.
So, the number of moles of H3PO4 can be calculated as:
Number of moles of H3PO4 = 1/3 * Number of moles of NaOH
Calculating:
Number of moles of H3PO4 = 1/3 * 0.0119646 mol = 0.0039882 mol (rounded to 5 decimal places)
Finally, to find the molarity of the phosphoric acid solution, divide the number of moles of H3PO4 by the volume of the phosphoric acid solution used in the titration:
Molarity of phosphoric acid solution = Number of moles of H3PO4 / Volume of phosphoric acid solution (in liters)
Given:
Volume of phosphoric acid solution = 32.3 mL = 0.0323 L
Calculating:
Molarity of phosphoric acid solution = 0.0039882 mol / 0.0323 L ≈ 0.1234 M (rounded to 4 decimal places)
Therefore, the molarity of the phosphoric acid solution is approximately 0.1234 M.