Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
State the composition of clean, dry air as approximately 78% nitrogen, ( N_2 ), 21% oxygen, ( O_2 ) and the remainder as a mixture of noble gases and carbon dioxide, ( CO_2 )
Describe tests to identify the gases: (a) ammonia, ( NH_3 ), using damp red litmus paper (b) carbon dioxide, ( CO_2 ), using limewater (c) chlorine, ( Cl_2 ), using damp litmus paper (d) hydrogen, ( H_2 ), using a lighted splint (e) oxygen, ( O_2 ), using a glowing splint (f) sulfur dioxide, ( SO_2 ), using acidified aqueous potassium manganate(VII)
