# (a) Interpretation: The counting rate 9cpm is the background counting rate in the laboratory which was measured at the time period of 3 min and it is required that the value of standard relative deviation should be less than the 5% ( σ R c / R c &lt; 0.05 ) . The total number of count is to be determined when the counting rate is 50cpm. Concept introduction: The formula for the standard deviation for the corrected counting rate is given as- σ R c = R x t x + R b t b ……. (1) Where, R x = counting rate for sample R b = counting rate for background t x = time required for counting rate for sample t b = time required for counting rate for background σ R c = standard deviation for the corrected counting rate Relative standard deviation is represented by the following formula- = σ R c R c …… (2) Also, R c = R x − R b ### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213 ### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

#### Solutions

Chapter 32, Problem 32.8QAP
Interpretation Introduction

## (a)Interpretation:The counting rate 9cpm is the background counting rate in the laboratory which was measured at the time period of 3 min and it is required that the value of standard relative deviation should be less than the 5% (σRc/Rc<0.05). The total number of count is to be determined when the counting rate is 50cpm.Concept introduction:The formula for the standard deviation for the corrected counting rate is given as-σRc=Rxtx+Rbtb ……. (1)Where,Rx = counting rate for sampleRb = counting rate for backgroundtx = time required for counting rate for sampletb = time required for counting rate for backgroundσRc = standard deviation for the corrected counting rateRelative standard deviation is represented by the following formula-=σRcRc …… (2)Also,Rc=Rx−Rb

Interpretation Introduction

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