Here are mass spectrometric signals for methane in H_2. CH_4 (vol %) 0 0.062 0.1

Question

Here are mass spectrometric signals for methane in H_2. CH_4 (vol %) 0 0.062 0.122 0.245 0.486 0.971 1.921 Signal (mV): 9.1 47.5 95.6 193.8 387.5 812.5 1671.9 (a) Subtract the blank value (9.1) from a signal values. Then use the method of least squares to find the slope and intercept. Don't forget to include the blank in your least squares analysis. (b) Replicate measurements of an unknown gave 152.1, 153.3, 153.9, and 155.7 mV, and a blank gave 7.8, 9.4, 10.6, and 7.0 mV. Subtract the average blank from the average unknown to find the average corrected signal for the unknown. (c) Find the concentration of the unknown.

Explanation / Answer

The slope is 867.41mv/Vol(%) and intercept = -19.85 mV

Average of unknown = (152.1+153.3+153.9+155.7)/4=153.75

                               Average of blank= (7.8+9.4+10.6+7)/4= 8.7

                              After subtracting blank, value = 153.75-8.7= 145.05 mV

From Equation, signal (mV)= 867.41* Vol%- 19.85

145.05= 867.41* Vol%-19.85

Vol%= (145.05+19.85)/ 867.41=0.19

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