What volume of oxygen will be left unreacted when \(250 \mathrm{~cm}^3\) of hydrogen and \(200 \mathrm{~cm}^3\) of oxygen are missed and exploded in a eudiometer?
A. \(75 \mathrm{~cm}^3\) B. \(125 \mathrm{~cm}^3\) C. \(325 \mathrm{~cm}^3\) D. \(50 \mathrm{~cm}^3\)
Correct Answer: A
Explanation
\(\begin{array}{cccc}2 \mathrm{H}_{2(\mathrm{~g})} & +\mathrm{O}_{2(\mathrm{~g})} \rightarrow & \rightarrow & 2 \mathrm{H}_2 \mathrm{O}_{(\mathrm{g})} \\ 2 & : 1 & \vdots & 2 \\ 250 \mathrm{~cm}^3 & : 125 \mathrm{~cm}^2: & 250 \mathrm{~cm}^3 \\ 250 \mathrm{~cm}^3 \text { of } \mathrm{H}_2 & \text { will require just } 125 \mathrm{~cm}^3 \text { of } \mathrm{O}_2 .\end{array}\) Since we are given \(200 \mathrm{~cm}^3\) of \(\mathrm{O}_2\), volume of unused \(\mathrm{O}_2=200 \mathrm{~cm}^3-125 \mathrm{~cm}^3=75 \mathrm{~cm}^3\)
