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AI 24% Sun 11:15 PM a Edit View History Bookmarks People Window Help Mastering Chemistry: Homework 29 Secure https://session.masteringchemistry.com/myct/itemview?assignmentProblemID 81024473&offset; prev I close CHM2046, Spring 2017 Period 5 Item 2 previous I 2 of 5 l next Item 2 Part B A battery is constructed based on the oxidation of What is the voltage of the battery after delivering 4.8 A for 70 h magnesium and the reduction of Cu .The initial concentrations of Mg and Cu are 1.1K10 M and 1,4 M in 1.0-liter half-cells. Submit My Answers Give up Part C How long can the battery deliver 48 A before going dead? Express your answer using two significant figures. ARSON emistry Submit My Answers up Ghen Continue

Explanation / Answer

Part B)

we do this by calculating charge, which is current multiplied by time

Q = i t = 4.8 x 7 x 60 x 60

    = 120960 C

no. of faradays = 120960 / 96485 = 1.254

since the reaction requires 2 moles of electrons / mole of each specie

Mg +2 + 2e- ---------> Mg ,

so the change in concentration of each specie = 1.254 /2 = 0.627 M

So we can say that 0.745 mole of Mg2+ ions are produced by oxidation and 0.745 moles of Cu2+ ions are reduced. The new concentrations are

Cu+2 = 1.4 - 0.627 = 0.773 M

Mg+2 = 1.1 x 10^-4 + 0.627 = 0.62711 M

Ecell = 2.71 - 0.05916 / 2 log [0.62711 / 0.773]

voltage = 2.71 V

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