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How many grams of silver could be placed out on a shild by electrolysis of a solution containing Λ° ions for a period of 4 hours by a current strength of 8.5 amperes? [F = 96,500 C mol–1, Molar mass of Ag = 107.8 g]


Molar mass of silver 107.8g
Current = 8.5 A
Ag++e Ag(s)

m=Z×I×t   = 107.896500×8.5 amp × 4 ×60 ×60m = 131947.2965  = 136.73 g.
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Calculate the resistance offered by 0.5 M CH3COOH solution when its molar conductivity. is 7.4 Ω–1 cm2 mol–1 and the cell constant is 0.037 cm–1.

We have gien the molar conductivity 7.4Ω–1 cm2 mol–1
cell constant 0.037cm-1
thus by using formula
k = 1R×lA
and therefore
                      R = 1k×lAk = Λm × C    = 7.4 Ω-1 cm2 mol-1 × 0.5 mol/L     = 7.4 Ω-1 × 0.05 mol1000 cm3     = 3.7 × 10-4 Ω-1 cm-1.
∴     R = 1k.la
              = 13.7 × 10-4Ω-1 cm-1×0.037 cm-1 = 100 Ω.
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Write the Nernst equation and calculate the emf of the following cell at 298 K : Cu(s) | Cu2+ (0.130 M) || Ag+ (1.00 x 10–4 M) | Ag(s)

Cu2+/ cu = + 0.34 V and E°Ag+/Ag = + 0.80 V.
Cu+2Ag+ Cu2++2Ag(s)Applying the nernst equation E = E°-0.0592logCu2+Ag+2E° = E°cathode - E°anode      = 0.80 - 0.34 = 0.46 VE = 0.46 - 0.0592log0.1301.0×10-4     = 0.46-0.0592×1.30×107     = 0.46 - 0.21 = 0.25 V.
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Conductivity of 0.00241 M acetic acid is 7.896 x 10–5 S cm–1. Calculate its molar conductivity, if Λ° for acetic acid is 390.5 S cm2 mol–1, what is its dissociation constant?

We have given that 
Concentration = 0.00241M
Conductivity  =0.00241S Cm-1
thus by using the formula
we get 

 = K×1000CC = 0.00241 MK = 7.896 × 10-5S cm-1 = 7.896 × 10-5× 10000.00241 = 32.76α = 0 = 32.76390.5 = 0.084K = 21-α = 0.00241×(0.084)2(1-0.084)      = 1.856 × 10-5.
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Calculate the equilibrium constant for the reaction,
Cu(s) + 2Ag+ (aq) → Cu2+ (aq) + 2Ag(s)
[E°cell = 0.46 V]
(T = 298 K, F = 96500 C mol–1, R = 8.31 J K–1 mol–1)


Using the formula we get:

G° = -nFE°cell           = -2.303 RT log Klog K = nFE°cell2.303×R×T          = 2×96500×0.462.303×8.31×298 = 15.5     K = 3.69×1015.
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