A chemist must prepare 550.0 ml of hydrochloric acid solution with a pH of 1.60 at 25°C. He will do this in three steps: Fill a 550.0 ml volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (8.0M) stock hydrochloric acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrochloric acid that the chemist must measure out in the second step. Round your answer to significant digits.

Question

Chemistry

Dillon

20 January, 18:34

A chemist must prepare 550.0 ml of hydrochloric acid solution with a pH of 1.60 at 25°C. He will do this in three steps: Fill a 550.0 ml volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (8.0M) stock hydrochloric acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrochloric acid that the chemist must measure out in the second step. Round your answer to significant digits.

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Answers (1)

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Judith Sweeney · Answer 1

Vol concentrated HCl needed = 1.73 ml

Explanation:

Prep 550 ml of HCl (aq) solution with pH = 1.60 at 25°C using 8M stock concentrate.

[HCl] = [H⁺] = 10⁻¹°⁶⁰M = 0.0251M HCl (aq)

Molarity Concentrate x Volume Concentrate = Molarity Dilute x Volume Dilute

8M x Vol Conc. = 0.0251M x 550ml

Vol Conc needed = 0.0251M x 550 ml / 8M = 1.73 ml of concentrate

Mixing = > to the quantity of water in the mixing flask transfer 1.73 ml of the 8M HCl concentrate solution and dilute up to but not to exceed the calibration mark on the mixing flask.