Question 4 of 5. >

Macmillan Learning

The absorbance at 470 nm of the Fe(II)-phenanthroline complex was measured for several different Fe²+ concentrations to

create a calibration curve. The absorbance at each Fe²+ concentration was measured five times. The absorbance values, already

corrected for the blank absorbance, are shown in the table.

[Fe²+] (µm)

75.9

53.5

37.7

15.2

182.3

45.575

m=

0.4152

A₁ A₂ A3 A₁ As

0.582 0.591 0.587 0.583 0.588

0.412 0.411 0.421 0.414 0.418

0.264 0.266 0.269 0.258 0.266

0.109 0.113 0.108 0.115 0.111 0.1112

1.367 1.381 1.385 1.370 1.383 1.377

0.2646

average:

0.3418 0.345 0.346 0.343 0.346 0.3443

Use the averages of the replicate absorbance measurements to determine the slope and y-intercept of the best-fit straight line.

b=

sum:

0.00793

0.177

Incorrect

average y, (, - y)²(x₁ - x)²

0.0585 919.6

0.5862

62.8

62.0

Attempt 2

0.0050

0.0063

0.0543

0.1242

922.6

1967

HM-1