JEE PYQ: Electrochemistry Question 13
Question 13 - 2020 (03 Sep Shift 1)
The photoelectric current from Na (work function, $w_0 = 2.3$ eV) is stopped by the output voltage of the cell Pt(s)|H$_2$(g, 1 bar)|HCl(aq., pH = 1)|AgCl(s)|Ag(s). The pH of aq. HCl required to stop the photoelectric current from K ($w_0 = 2.25$ eV), all other conditions remaining the same, is ____ $\times 10^{-2}$ (to the nearest integer).
Given: $2.303\frac{RT}{F} = 0.06$ V; $E^0_{\text{AgCl|Ag|Cl}^-} = 0.22$ V
Show Answer
Answer: 142
Solution
For Na: $E_{\text{cell}} = 0.34$ V, photon energy $= 2.64$ eV. For K: $(KE){\max} = 0.39$ eV = $E{\text{cell}}$. Solving: pH = 17/12 = 1.4166 = $142 \times 10^{-2}$.
BETA
