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Problem Set 2 Solutions

# Problem Set 2 Solutions - C hemistry 2101 I ntroductory...

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Chemistry 2101 Introductory Analytical Chemistry Fall 2009 Solutions Problem Set 2 Chapter 4 Problem 4-1 The larger the precision, the smaller the standard deviation. The accuracy and standard deviation are not necessarily related. Problem 4-2 0.683, 0.955, 0.997 Problem 4-3 (a) Mean = 1.52767 (b) Standard deviation = 0.00126 {note degrees of freedom: 8-1} Relative standard deviation (0. 00126/1.52767) x 100 = 0.0825% (c) μ = x ± t s n = 1.52793 ± 3.707 ( ) 0.00007 ( ) 7 = 1.52793 ± 0.00010 Problem 4-4 (a) The region around the measured mean in which the true mean is likely to lie is called the confidence interval. (b) A 95% confidence interval is necessarily larger than a 90% confidence interval. The only way to increase the probability of finding the true mean in the interval is to increase the size of the interval. Problem 4-5 mean = 108.6 standard deviation = 7.1 90% confidence interval = 108.6±6.8 Problem 4-6 s pooled = 0.0004 49 t = 2. 32 Because the calculated t is larger than the tabulated t (2.306), the difference is significant. Problem 4-9 For indicators 1 and 2: s pooled = 0.0018648 t = 15.60

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