Answers to Problems
Chapter 2
(2) (a) 25.47 cm^3
(b) Q experimental (90% level) for highest value (25.80 cm^3 ) is 0.58. This result should be rejected.(c) 25.40 cm^3(3) x = 5.35; Sn– 1 = 0.0178. Relative standard deviation = 0.33%
(4) Overall mean = 9.67 ppm; pooled = 0.186 ppm
(5) CI (90%) = 5.353 ± 0.017
(6) F = 2.25 (Fcritical (45%) = 9.12) (S 1 = 0.055); (S 2 = 0.0082). Precisions are similar.
(7) t = 3.97 Determinate error indicated with between 99.0 and 99.9% confidence.
(8) t = 6.76, greater than 99.9% confidence that a difference exists. Thus the mixing is unsatisfactory.
(9) Apply Q-test, reject 0.60; t = 1.21. The difference is significant at less than 90% confidence and the
new method may be used.
(10) Method 1: Positive constant error
Method 2: Small negative proportional error(11) y = 0.8x + 0.2. A straight line plot is justified, but the precision of the measurements is very poor.
The importance of using a scatter plot in reviewing the data as well as a least squares calculation is
illustrated.
(12) y = 0.0193x + 0.0152. This is a satisfactory calibration curve although it does not pass through the
origin.
Chapter 3
(1) 0.175 M
(2) pH = 3.575
(3) pH = 9.15
(4) pH = 5.65
Chapter 4
(1) (a) 1833 cm^3 ; (b) 4