Wilfrid Laurie University x G O biscms/mod/ibis/view.php?id 21273 www.saplinglea

Question

Wilfrid Laurie University x G O biscms/mod/ibis/view.php?id 21273 www.saplinglearning.ca/i 2/17/2017 11:55 PM A 81.8/100 2/17/2017 12:45 PM Gradebook Attempts Score Print Calculator Periodic Table Question 9 of 11 Map Sapling Learning Atomic emission spectroscopy and the method of standard addition are used to detemine the Na in an unknown sample, Increasing amounts of a 1.75 ug/mL standard Na solution are added to a series of volumetric flasks containing 15.00 mL of the unknown solution, The volumetric flasks are then diluted to a final volume of 200,0 mL. Atomic emission spectroscopy is then used to measure the emission intensity of each solution Unknown Volume (mL) Standard Volume (mL) Final Volume (mL) Emission Intensity 15.00 0.00 200.0 3420 15.00 5.00 2000 4650 15.00 10.00 2000 6330 15.00 15.00 200.0 708.0 15.00 20.00 200.0 Based on the data in the table above, determine the original concentration of Na as well as its uncertainty in the unknown sample. Report the uncertainty with three significant figures. Concentration Uncertainty ug/ mL ools O Previous 3 Give Up & View Solution Check Answer Next Exit Ask me anything A Assignment Information Available From 1/3/2017 06:0C 2/17/2017 11:5 Due Date Points Possible: 100 Grade Category: Default Description: Policies Homework You can check your answers. lutions when you c Yo up on any question You can keep trying to answer each you get it right or give up You lose 5% of the points available your question for each incorrect O eTextbook O Help With This Topic O Web Help & Videos O Technical Support and Bug Repo 1.25 PM ENG 2017-02.

Explanation / Answer

Concentration of standard in diluted solutions,

with 0 ml standard added = 0 ug/ml

with 5 ml standard added = 5 x 1.75/200 = 0.04375 ug/ml

with 10 ml standard added = 10 x 1.75/200 = 0.0875 ug/ml

with 15 ml standard added = 15 x 1.75/200 = 0.13125 ug/ml

with 20 ml standard added = 20 x 1.75/200 = 0.175 ug/ml

Let Cx be the concentration of Na+ in unknown solution then,

Cx/(Cx + 0.175) = 342/939

939Cx = 342Cx + 59.85

Cx = 0.10025 ug/ml

Doing the same calculation for all the data,

Cx

0.104633

0.102835

0.098438

0.100250

Uncertainty = 0.00129 ug/ml

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.