In the laboratory preparation of ammonia, the flask is placed in a slanting position so as to

Analyze the question: In the lab preparation of ammonia, the flask is tilted (slanted) with its mouth pointing slightly downward. We need to know why.

Concept: Ammonia is prepared by heating a solid mixture of an ammonium salt and a base:

2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃

Water vapour is produced as a by-product. When the mixture is heated, this steam condenses on the cooler upper parts of the flask's walls.

Solution:

1. The reactants are solids, so there is no "mixing" issue as with liquids. This rules out B.
2. The tilt has nothing to do with the reaction rate, which depends on temperature and the reactants. This rules out C.
3. No precipitate is formed, because the reaction is between solids and gives gaseous and liquid products. This rules out D.
4. If the flask were upright, the condensed water would trickle back down onto the hot glass at the bottom. The sudden cooling would cause the glass to crack. By tilting the flask with its mouth downward, the water runs toward the mouth and out, away from the hot part of the glass.

This is the same reason a boiling tube is tilted when heating a solid that gives off moisture.

Answer: A. It prevents condensed water from breaking the reaction flask.

Tip: Whenever you heat a solid that releases water, remember "mouth down, water out." The tilt protects the hot glass from the water. The question about a slanted flask in ammonia preparation is a recurring JAMB item.