Question

A student conducts the following demonstration: A 15-g sample of NaHCO3 is placed in a test tube. The bottom of the test tube is heated with an open flame. Condensation forms on the inside walls of the test tube. A burning splint is extinguished when placed at the mouth of the test tube. What can the student conclude after conducting this demonstration?

Answer 1

Question:

Options

A. The burning splint was extinguished because of a lack of CO2 in the

test tube.

B. The burning splint was extinguished because of a lack of H2O vapor.

C. Decomposition produced CO2 and H2O.

D. Combustion produced O2 and H2O

Answer:

C. The decomposition produced CO₂ and H₂O

Explanation:

Sodium hydrogen carbonate NaHCO₃, also known as baking soda or sodium bicarbonate which is a white crystalline solid that appears as a fine powder, decomposes when heated above 80 °C to form sodium carbonate, water and carbon dioxide as follows;

2NaHCO₃(s) → Na₂CO₃ (s) + H₂O(g) + CO₂(g)

At 400 °C, Na₂CO₃ decomposes further to form more carbon dioxide as follows

Na₂CO₃(s) → Na₂O (s) + CO₂ (g).