1Question 1: Find the algebraic answer and absolute uncertainty and express each

Question

1Question 1: Find the algebraic answer and absolute uncertainty and express each answer with the correct amount of significant figures. 2.4 (± 0.5) 4.7 (± 0.1) × 5.5 (± 0.4) =______±_______ 2.Five solutions were prepared in 10 mL volumetric flasks by adding 5 mL of unknown to the given volume of stock solution and diluting to 10 mL with acetic acid. Using a standard addition experiment set up, students plot their data on fluorescence vs. standard concentration (ppm), and find this information from the line: y = 0.0179x 0.101 a) Calculate, to three sig figs, the concentration of unknown in the solutions prepared. b) Calculate to three sig figs, the undiluted concentration of unknown. 3. The following is a description of the preparation of an unknown sample: Solution 1. 0.0519g of an unknown Fe2 salt is measured and added to a 25 mL volumetric flask. 1.0 mL of 6 M HCl is added before diluting to volume. Solution 2. 1.0 mL of Solution 1 is then transferred to a 100 mL volumetric flask. 1.25 mL of buffer and 5.0 mL of ferrozine is added before diluting to volume. The absorbance of Solution 2 is measured to be 0.895. Report all answers to 3 sig figs.

Explanation / Answer

Answer1:

Algebric answer: As no sign is present between 2.4 and 4.7, I am assuming +

So, 2.4 + 4.7 x 5.5 = Using BODMAS = 28.25 = 28 ( two significant numbers)

uncertainity= [(5.5+0.4) x (4.7+0.1)+(2.4+0.5)] - [(5.5-0.4) x (4.7-0.1)+(2.4-0.5)] = 31.22 -25.36 = 5.9

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