In two separate experiments,the same quantity of electricity was passed through silver and gold solutions. The amounts of $Ag$ and $Au$ deposited are $2.15 \ g$ and $1.31 \ g$,respectively. The valency of gold is [Atomic mass of $Ag = 107.9$; $Au = 197$].

$7.5 \ A$ current is passed for $200 \ s$ through $AgNO_3$ solution. If experimentally $1.08 \ g$ of $Ag$ is obtained,then calculate the current efficiency (cell capacity). $[Ag = 108 \ u]$

How many grams of cobalt metal will be deposited when a solution of cobalt $(II)$ chloride is electrolyzed with a current of $10 \ A$ for $109$ minutes? ($1 \ Faraday = 96,500 \ C$; Atomic mass of $Co = 59 \ u$)

Electricity is passed through an acidic solution of $Cu^{2+}$ until all the $Cu^{2+}$ is exhausted, leading to the deposition of $300 \ mg$ of $Cu$ metal. Subsequently, a current of $600 \ mA$ is passed through the same solution for another $28 \ minutes$ while keeping the total volume of the solution fixed at $200 \ mL$. The total volume of oxygen evolved at $STP$ during the entire process is . . . . . . $mL$. (Nearest integer) [Given: $Cu^{2+}_{(aq)} + 2e^{-} \rightarrow Cu_{(s)}$, $E_{red}^0 = +0.34 \ V$; $O_{2(g)} + 4H^{+} + 4e^{-} \rightarrow 2H_2O$, $E_{red}^0 = +1.23 \ V$; Molar mass of $Cu = 63.54 \ g \ mol^{-1}$; Faraday Constant $= 96500 \ C \ mol^{-1}$; Molar volume at $STP = 22.4 \ L$]

When the same quantity of electricity is passed through aqueous $AgNO_3$ and $H_2SO_4$ solutions connected in series,$5.04 \times 10^{-2} \ g$ of $H_2$ is liberated. What is the mass of silver (in grams) deposited? (Eq. wts. of hydrogen $= 1.008$,silver $= 108$)

$A$ steady current of $5 \, A$ is maintained for $45 \, min$. During this time,it deposits $4.572 \, g$ of zinc at the cathode of a voltameter. The $E.C.E.$ of zinc is: