0.5 g of an organic compound (X) with 60 % carbon will produce __________ × 10⁻¹ g of CO₂ on complete combustion.

Solution

Chemistry ma’am · 3 steps

Every carbon atom ends up in CO₂, so find the carbon mass first and scale it by 44/12.

1. Mass of carbon. The compound is 60% carbon, so 0.5 g of it contains 0.60 × 0.5 = 0.3 g of carbon.
2. Carbon goes to CO2. On complete combustion all of this carbon becomes CO₂. Each 12 g of carbon gives 44 g of CO₂, one mole of each.

   m_(CO₂) = 0.3 g × 44/12 = 1.1 g

3. So. 1.1 g = 11 × 10⁻¹ g, so the answer is 11.

The common slip: 1.1. Entering the mass in grams gives 1.1, but the blank is in units of 10⁻¹ g, so 1.1 g must be written as 11.

The idea to keep. In combustion questions, carbon is conserved: mass of CO₂ = mass of C × 44/12. For hydrogen, mass of H₂O = mass of H × 18/2.

Answer from the NTA final answer key. Solution by PrepWiser.