and so... 1. Recall from high school or first-year college chemistry that pH-meters are typically standard equipment in the labs. If you were asked to measure the pH of a solution and use that pH reading to calculate the IH"} concentration in that solution, the calculations should be straightforward. As you recall... pH = -log[H] [H1 - 10- Many pH meters display pH to the second decimal place. Thus, a good, steady reading on the pH meter would seem to have an uncertainty of 0.01 pH units. Suppose you arrive late to lab and the only pH meter left is the older model with the display that seems to "jump around". Of course, the person that annoys you the most in this lab is right across from you and has the newer pH meter that has a fairly steady pH readout. You are all given aliquots (samples) of the same solution and everyone repeats the pH measurement several times and reports a mean (average) and a standard deviation. Here are your results and those of the annoying person: You # Measurements Mean (avg) pH Std. Dev. 5 8.34 0.19 Annoying person # Measurements 5 Mean (avg) pH 7.81 Std. Dev. 0.02 We will cover means and standard deviations in great detail in Chapter 4. For now, just consider the standard deviations to be absolute uncertainties from random errors. Thus, the properly reported values would be: You pH = 8.3. (10.19) Annoying person pH = 7.81 (+0.02) (2) a) Why is the pH for "You" above reported to only 2 significant figures while 3 significant figures are retained for the "Annoying Person"? C1604 5) b) Determine and properly report the [H") and the associated absolute uncertainties for the solution from the reported pH values for both You and the Annoying Person. (Hint: There is an example problem on the bottom o p. 57 in the text that is similar.) 2