Chemical Properties of Carbon Compounds (Combustion, Oxidation, Addition, Substitution) MCQs

Q1. Which gas turns lime water milky and is used to test for its presence?

• A.Carbon dioxide
• B.Hydrogen
• C.Oxygen
• D.Nitrogen

Answer: A. Carbon dioxide

Q2. Dry hydrogen chloride (HCl) gas is tested with dry blue litmus paper and then with moist blue litmus paper. What is observed?

• A.No change with dry litmus (stays blue); turns red with moist litmus
• B.Turns red with both dry and moist litmus
• C.No change with either dry or moist litmus
• D.Turns blue with both

Answer: A. No change with dry litmus (stays blue); turns red with moist litmus

Q3. What would be the electron dot structure of carbon dioxide which has the formula CO2?

• A.O=C=O
• B.O=C-O
• C.O-O=C
• D.O=C-O-O

Answer: A. O=C=O

The core fact here is - O=C=O. That fits the listed correct option directly - Correct electron dot structure for CO2. Looking at the others: option B) 'O=C-O' fails since Incorrect electron dot structure for CO2; option C) 'O-O=C' is incorrect: Incorrect electron dot structure for CO2. Hence the answer is A) O=C=O.