68. Hydrochloric acid is coulometrically titrated with electrogenerated OH– ions at a current strength of 10 mA. The equivalence point when titrating five samples with a volume of 5 ml of the test solution is reached in the time:
Sample no. 1 2 3 4 5
time 3 min 10 s 3 min 15 s 3 min 17 s 3 min 12 s 3 min 12 s
Determine the equivalent (normal) concentration of the solution and the relative measurement error at a confidence level of 0.95.

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