A student while trying to identify two gases labeled \(A\) and \(B\), found that gas A is acidic to litmus paper and turn acidified potassium dichromate solution green, while gas B turns red litmus paper blue and forms dense white fume with hydrogen chloride. The correct identity of \(A\) and \(B\) respectively are ____________
A. \(CO _{2}\) and \(N _{2}\) B. \(SO _{2}\) and \(NH _{3}\) C. \(HCl\) and \(NH _{3}\) D. \(NO _{2}\) and \(PCl _{5}\)
Correct Answer: B
Explanation
For A to be acidic to litmus, it is likely to be \(SO _{2}\) and \(HCl\) both of which are acidic. Because A decolourizes (reduces) acidified potassium dichloromate, it must be a reducing agent, and so is \(SO _{2}\) and not \(HClOnly NH _{3}\) forms dense white fume with hydrogen chloride. So, A and B respectively are \(SO _{2}\) \& \(NH _{3}\).
