Analytical Chem istry - DePauw University

204 Analytical Chemistry 2.00.1478x-intercept =− =−1.731 mL-10.0854 mLPlugging this into the equation for the x-intercept and solving for C A givesthe concentration of Mn 2+ asC mLx-intercept=− 3 478 mL =− × 25 00.A.100.6 mg/ LFor Figure 7b, the x-intercept is= 696 .0.1478x-intercept =− =−3.478 mL-10.0425 mLand the concentration of Mn 2+ ismg/LC mLx-intercept=− mL =− × 25 003.478A.= 6 .96 mg/L50.00 LClick here to return to the chapter.Practice Exercise 5.4We begin by setting up a table to help us organize the calculation.x i y i x i y i2x i0.000 0.00 0.000 0.0001.55×10 –3 0.050 7.750×10 –5 2.403×10 –63.16×10 –3 0.093 2.939×10 –4 9.986×10 –64.74×10 –3 0.143 6.778×10 –4 2.247×10 –56.34×10 –3 0.188 1.192×10 –3 4.020×10 –57.92×10 –3 0.236 1.869×10 –3 6.273×10 –5Adding the values in each column gives∑ x i= 2.371×10 –2i∑ y i= 0.710i∑ xy i i= 4.110×10 –3 2∑ x i= 1.278×10 –4iSubstituting these values into equation 5.17 and equation 5.18, we findthat the slope and the y-intercept are6 4 110 10 2 371 10 0 710= × ( . × ) − ( . × ) × ( . )= 29.57−4 −2 2( 6×1.378× 10 ) − ( 2. 371×10 )−3 −2b 1i