Mary determined the quantity of K+ (39.898g/mol) in coconut water by means of th

Question

Mary determined the quantity of K+ (39.898g/mol) in coconut water by means of the atomic absorption technique. With that purpose, she determined a calibration curve measuring the absorbance of standard solutions in a range of 1ppm to 18 ppm. The equation of the curve of calibration she acquired was y=0.0670x +0.03001, R=0.9998. Using this information, answer the following question: What is the molar concentration of K+ in the coconut water sample if she measured absorbance three times, obtaining the following values: 0.532, 0.531, 0.529 ? Mary determined the quantity of K+ (39.898g/mol) in coconut water by means of the atomic absorption technique. With that purpose, she determined a calibration curve measuring the absorbance of standard solutions in a range of 1ppm to 18 ppm. The equation of the curve of calibration she acquired was y=0.0670x +0.03001, R=0.9998. Using this information, answer the following question: What is the molar concentration of K+ in the coconut water sample if she measured absorbance three times, obtaining the following values: 0.532, 0.531, 0.529 ?

Explanation / Answer

Given Calibration curve will give a linear realtionship between the absorption values and the concentration of K+

y = 0.0670 x + 0.03001

Given absorbance x = 0.532, 0.531, 0.529

so y(0.529) = 0.0670 * 0.529 + 0.03001 = 0.065453 M

y(0.531) = 0.0670 * 0.531 + 0.03001 = 0.065587 M

y(0.532) = 0.0670 * 0.532 + 0.03001 = 0.065654 M

Average concentration = 0.0655647 M

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