20 pls You are correct. Previous Tries r receipt no. is 168-3367 19. Shown below

Question

20 pls

You are correct. Previous Tries r receipt no. is 168-3367 19. Shown below is the standard line notation for a concentration cell: Cu(s)Cu (0.20 M)lCu (0.30 M)|Cus) Determine the value of Q and E for this cell: Incorrect Q0.67; E -5.2 x 103v Incorrect Q-0.67; E- 0 V Incorrect Q= 1.5; E=-5.2 x 10.-v Correct: Q 0.67; E- 5.2 x 10-3 v Incorrect Q 1.5; E- 5.2 x 103 v You are correct. Previous r receipt no. is 168-2712 20. Consider the following half-reactions at 298 K: Fe--+ 2e- Fe ed 0.441 v Ered-0.403 v A galvanic cell based on these half-reactions is set up under standard conditions where each solutions is 1.00 L and each electrode weighs exactly 100.0g. How much will the Cd electrode weigh when the non- standard potential of the cell is 0.03195 V? 115 Submit Answer Tries 2/3 Previous Tries 21. A voltaic cell can be set up using the following pair of half-reactions at 298 K: I2 (s) 2e 2I (aq) Fe2 (aq) +2e- Fe (s)

Explanation / Answer

molar mass of Fe is 55.84 g/mol

molar mass of Cd is 112.41 g/mol

calculate the moles of Fe with moles = mass / molar mass

moles Fe = 100 / 55.84 = 1.79

moles of Cd

moles Cd = 100 / 112.41 =0.8896

since there is 1 liter of solution then the moles is equal to the molarity

[Fe] = 1.79 M

[Cd] = 0.8896 M

after the reaction theconcenntration of Fe is

[Fe] = 1.79 + x

[Cd] = 0.8896 - x

E cell = Ered - Eox

E ocell = - 0.403 - (-0.441) = 0.038 V

Apply the nernst equation

E cell = Eo cell - 0.0592/n * log Q

n is the number of electrons being exchanged ( 2 in this case)

Q is the ratio of products to reactants

Q = [Fe+2] / [Cd+2]

we know from the statement that E cell is 0.03195 V so

0.03195 = 0.038 - 0.0592/2 * log (1.79 + x / 0.8896 - x )

rearrange this to get

-0.00605 *2 = -0.0592 *  log (1.79 + x / 0.8896 - x )

0.20439 = log (1.79 + x / 0.8896 - x )

100.20439 = 1.79 + x / 0.8896 - x

1.6 (0.8896 - x) = 1.79 + x

1.4233 - 1.6x = 1.79 + x

-2.6 x = 1.79 - 1.4233 = 0.366

x = 0.366 / -2.6 =- 0.1406

Concentration of Fe is

1.79 - 0.14061 = 1.649

concentration of Cd

0.8896 + 0.14061 = 1.03

moles off Cd = 1.03 moles

grams of Cd is moles * molar mass so

grams Cd = 1.03 * 112.41 = 115.8068 grams

*Use a spreadsheet for this calculations =)

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