A fossil coal containing 80% C, 8% H2, 2% O2, 1% S, 2% N2, 3% H2O and 4% ash, burns with 60% excess O2. Details: H-1, C-12, N-14, O-16, S-32
MAR = 28.84 g / mol
R = 62.3 mmHg. L / mol / K

Questions:
a) The mass of air fed.
b) The volume of air fed at 27°C and 720 mmHg.
c) The mass of smoke.
d) The volume of fumes on a wet basis, measured at 120 ° C and 720 mmHg.
e) The probable ORSAT analysis of the fumes.
f) The BM by weight of the combustion.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

the answer is option a.