Which of the following is true if gasoline is burnt in perfect air/fuel stoichiometric ratio in internal combustion engines? (A) Fuel consumption decreases. (B) Power of engine remains optimum. (C) NOx emission remains high compared to rich and lean fuel. (D) Hydrocarbon emission remains low. (E) Carbon monoxide emission decreases compared to rich fuel.
Choose the correct answer from the options given below:

Correct option is C

Explanation:
When gasoline is burnt at the stoichiometric air-fuel ratio (typically 14.7:1 for gasoline), the combustion is considered ideal, and the following happens:
· (A) Fuel consumption is optimized due to complete combustion.
· (B) The engine produces optimum power output at this ratio.
· (C) NOx (nitrogen oxides) emissions are high because of the higher combustion temperature at stoichiometric conditions.
· (D) Hydrocarbon emissions are low due to complete combustion of the fuel.
· (E) Carbon monoxide (CO) emissions decrease compared to rich fuel mixtures (where oxygen is insufficient).
Information Booster:
· Stoichiometric ratio is the ideal air-fuel ratio where all the fuel is burned using all available oxygen.
· Rich mixture: More fuel, less oxygen → more CO and hydrocarbons.
· Lean mixture: More oxygen, less fuel → low CO but possible misfires, high NOx.
· Perfect stoichiometric combustion leads to high temperatures, favoring NOx formation.
Additional Information:
· Option (a) is incorrect because it omits (C) and (D), which are true.
· Option (b) is incorrect because it omits (C) and (E).
· Option (d) omits (C), which is a valid point about NOx emissions.