Which of the following gases is a major contributor to the greenhouse effect?
A. Ammonia
B. Oxygen
C. Nitrogen
D. Carbon dioxide
Answer: Option D
Solution (By JKExamLibrary)
CO₂ is the primary anthropogenic greenhouse gas from fossil fuel combustion. N₂, O₂ not IR active. Ammonia is not a major GHG. Methane, N₂O also contribute.
Explanation:
A gel is a type of colloid where the dispersed phase is a liquid and the dispersed medium is a solid. Cheese, butter, and jellies are classic examples of gels. Milk is an emulsion (liquid in liquid), while fog and smoke are aerosols.
Explanation:
J.J. Thomson proposed the 'plum pudding' model (also called watermelon model) where the atom was considered a sphere of positive charge with electrons embedded like seeds. Rutherford's gold foil experiment disproved this by showing a dense, positively charged nucleus. Dalton proposed the indivisible atom theory. Bohr gave the model with discrete energy levels. Thomson discovered the electron but couldn't explain the nucleus.
Explanation:
NH₃ has a lone pair on nitrogen, which it donates to the empty 1s orbital of H⁺, forming a coordinate (dative) bond where both electrons come from nitrogen. The resulting NH₄⁺ has four equivalent N–H covalent bonds and a +1 charge. Coordinate bonds are common in complex ions: e.g., [Ag(NH₃)₂]⁺. Once formed, a coordinate bond is indistinguishable from a covalent bond.
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