32. A solution suspected of containing copper is analyzed. To determine the standard curve, the absorbance of five standards ranging from 0.125 mg/L Cu to 1.25 mg/L Cu was measured and graphed against the concentration. The slope of the linear best-fit line was determined to be 0.6136 and the y-intercept was 0.0142. If three samples of the unknown solution have absorbance values of 0.438, 0.434, and 0.439 what is the concentration of the unknown

Question

Daniela Brock

Chemistry

21 July, 23:06

32. A solution suspected of containing copper is analyzed. To determine the standard curve, the absorbance of five standards ranging from 0.125 mg/L Cu to 1.25 mg/L Cu was measured and graphed against the concentration. The slope of the linear best-fit line was determined to be 0.6136 and the y-intercept was 0.0142. If three samples of the unknown solution have absorbance values of 0.438, 0.434, and 0.439 what is the concentration of the unknown

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Mila Cowan · Answer 1

0.689 mg/L Cu

Explanation:

The equation of the best-fit line is:

y = 0.6136x + 0.0142

Where y is the absorbance and x is the concentration in mg/L.

Now using that equation we calculate x when y is equal to 0.438, 0.434 & 0.439.

1) 0.438 = 0.6136x + 0.0142

x = 0.691 mg/L

2) 0.434 = 0.6136x + 0.0142

x = 0.684 mg/L

3) 0.439 = 0.6136x + 0.0142

x = 0.692 mg/L

Finally we calculate the mean of the three concentrations:

(0.691 + 0.684 + 0.692) / 3 = 0.689 mg/L