A) 105,700 cal
B) 61,000 cal
C) 105,000 cal
D) 62,300 cal
Correct Answer: D
Solution :
Key Idea: Use Hesse?s law Given\[Zn+\frac{1}{2}{{O}_{2}}\xrightarrow{{}}ZnO+84000\,cal\] \[Hg+\frac{1}{2}{{O}_{2}}\xrightarrow{{}}HgO+21,700\,\text{cal}\] \[Zn+HgO\xrightarrow{{}}Hg+ZnO+heat\] \[\frac{1}{2}O\,Zn\xrightarrow{{}}ZnO+84,000\,\text{cal}\]\[\begin{align} & \underline{\,\,\,HgO\xrightarrow{{}}Hg+\frac{1}{2}{{O}_{2}}-21,000\,\text{cal}\,\,\,\,\,\,\,\,\,\,\,\,}\,\, \\ & Zn+HgO\xrightarrow{{}}ZnO+Hg+62,300\,\text{cal} \\ \end{align}\] \[\therefore \]Heat in reaction \[=+\,\,62,300\]
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