181.
The reduction potential ( in volt ) of a hydrogen electrode set up with a $$2 \times {10^{ - 2}}M$$ aqueous solution of a weak mono basic acid $$\left( {{K_a} = 5 \times {{10}^{ - 5}}} \right)$$ at one atmosphere and $${25^ \circ }C$$ is
Lower the value of reduction potential, stronger is the reducing agent i.e., undergoes oxidation most easily.
$$Cr \to C{r^{3 + }} + 3{e^ - }{\text{(oxidation)}}$$
Hence, $$Cr$$ is the strongest reducing agent.
183.
The specific conductance of a saturated solution of $$AgCl$$ at $${25^ \circ }C$$ is $$1.821 \times {10^{ - 5}}mho\,c{m^{ - 1}}.$$ What is the solubility of $$AgCl$$ in water $$\left( {{\text{in}}\,g\,{L^{ - 1}}} \right),$$ if limiting molar conductivity of $$AgCl$$ is $$130.26\,mho\,c{m^2}mo{l^{ - 1}}?$$
184.
The anodic half-cell of lead-acid battery is recharged using electricity of 0.05 Faraday. The amount of $$PbS{O_4}$$ electrolyzed in $$g$$ during the process is : ( Molar mass of $$PbS{O_4} = 303\,g\,mo{l^{ - 1}}$$ )
Half cell reaction : $$PbS{O_4} \to P{b^{4 + }} + 2{e^ - }$$
According to the reaction :
$$PbS{O_4} \to P{b^{4 + }} + 2{e^ - }$$
We require $$2F$$ for the electrolysis of 1 mol or $$303 g$$ of $$PbS{O_4}$$
∴ Amount of $$PbS{O_4}$$ electrolysed by $$0.05F$$
$$\eqalign{
& = \frac{{303}}{2} \times .05 \cr
& = 7.575\,g \approx 7.6\,g \cr} $$
185.
$$A{l_2}{O_3}$$ is reduced by electrolysis at low potentials and high currents. If $$4.0 \times {10^4}A$$ of current is passed through molten $$A{l_2}{O_3}$$ for $$6$$ $$h,$$ what mass of aluminium is produced? ( Assume $$100\% $$ current efficiency, atomic mass of $$Al = 27\,g\,mo{l^{ - 1}}$$ )
On dilution number of ions decrease in unit volume hence specific conductance decreases. But separation between ions also increase hence equivalent conductance increases.
189.
A weak monobasic acid is $$5\% $$ dissociated in $$0.01\,mol\,d{m^{ - 3}}$$ solution. Limiting molar conductivity of acid at infinite dilution is $$4 \times {10^{ - 2}}\,oh{m^{ - 1}}\,{m^2}\,mo{l^{ - 1}}.$$ What will be the conductivity of $$0.05\,mol\,d{m^{ - 3}}$$ solution of the acid?
A
$$8.94 \times {10^{ - 6}}\,oh{m^{ - 1}}\,c{m^2}\,mo{l^{ - 1}}$$
B
$$8.92 \times {10^{ - 4}}\,oh{m^{ - 1}}\,c{m^2}\,mo{l^{ - 1}}$$
C
$$4.46 \times {10^{ - 6}}\,oh{m^{ - 1}}\,c{m^2}\,mo{l^{ - 1}}$$
D
$$2.23 \times {10^{ - 5}}\,oh{m^{ - 1}}\,c{m^2}\,mo{l^{ - 1}}$$
190.
When during electrolysis of a solution of $$AgN{O_3}$$ 9650 coulombs of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be
When 96500 coulomb of electricity is passed through the electroplating bath the amount of $$Ag$$ deposited = $$108g$$
∴ when 9650 coulomb of electricity is passed deposited $$Ag.$$
$$\eqalign{
& = \frac{{108}}{{96500}} \times 9650 \cr
& = 10.8g \cr} $$