Q167 / 170 · Manipal (MET) 2021 · Physics
When 1 g hydrogen
( $E C E=1.044 \times 10^{-8} \mathrm{~kg} \mathrm{C}^{-1}$ ) forms water, 34 kcal heat is liberated. The minimum voltage required to decompose water is :
- A0.75 V
- B3 V
- Correct answerC1.5 V
- D4.5 V
Solution
$q=\frac{m}{z}=\frac{1 \times 10^{-3}}{1.044 \times 10^{-8}}=\frac{10^5}{1.044} C$
Given, $\mathrm{H}=34 \mathrm{k}-\mathrm{cal}=34 \times 10^3 \times 4.2 \mathrm{~J}$ Heat produced, $H=V q$ $\begin{aligned} & \therefore \quad 34 \times 10^3 \times 4.2=\frac{V \times 10^5}{1.044} \\ & \therefore \quad V=\frac{34 \times 10^3 \times 4.2 \times 1.044}{10^5}=1.5 \mathrm{~V}\end{aligned}$
Given, $\mathrm{H}=34 \mathrm{k}-\mathrm{cal}=34 \times 10^3 \times 4.2 \mathrm{~J}$ Heat produced, $H=V q$ $\begin{aligned} & \therefore \quad 34 \times 10^3 \times 4.2=\frac{V \times 10^5}{1.044} \\ & \therefore \quad V=\frac{34 \times 10^3 \times 4.2 \times 1.044}{10^5}=1.5 \mathrm{~V}\end{aligned}$
Hence, the correct answer is option: 'C'.