A set of standards is run for a set of NiCl_26H_2O solutions. The data is plotte

Question

A set of standards is run for a set of NiCl_26H_2O solutions. The data is plotted with absorbance on the y axis and the molarity of the nickel ion on the x-axis. The slope of the line is 2.78 M^-1 cm^-1 and the y-intercept is 0.04. A sample of 0.90 g of NiSO_4 with an unknown amount of water of hydration is dissolved in water to a final volume of 25.0 mL of water, and its absorbance is measured as 0.79. The pathlength was 1 cm. Calculate the concentration of nickel in the unknown sample. Select one: a. 0.24 M b. 2.08 M c. 0.30 M d. 0.27 M

Explanation / Answer

A = 0.79

A = 2.79*M + 0.04

for

0.79 = 2.79*M+0.04

M = (0.79-0.04)/(2.79) = 0.26881 mol per liter

so...

nearest answer is D, 0.27 M (roundin 0.268 to 0.27)

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