Which of the following gases is responsible for the formation of photochemical smog?
A. Methane
B. Ozone and PAN
C. Carbon dioxide
D. Ammonia
Answer: Option B
Solution (By JKExamLibrary)
Photochemical smog is formed in sunny, dry cities due to the reaction of sunlight with nitrogen oxides and volatile organic compounds (from vehicle exhaust). This produces secondary pollutants like ozone (O₃), peroxyacetyl nitrate (PAN), and aldehydes, which make up the harmful smog.
Explanation:
In PCl₅, phosphorus forms five covalent bonds with five chlorine atoms. Phosphorus has 5 valence electrons (3s²3p³), and by using d-orbitals, it can expand its octet to accommodate 5 bonds. Thus its covalency is 5. In PCl₃, it is 3. Valency is the number of bonds formed. The oxidation state of P in PCl₅ is +5.
Explanation:
Phenolphthalein is a synthetic acid-base indicator, organic compound prepared in the lab. Litmus is a natural dye from lichens. Turmeric is a natural indicator (yellow in acid, reddish brown in base). Red cabbage juice is natural. Synthetic indicators are often used in titrations: methyl orange, phenolphthalein.
Explanation:
At cathode (negative electrode), H⁺ ions are reduced: 2H⁺ + 2e⁻ → H₂(g). At anode (positive), water is oxidized: 2H₂O → O₂ + 4H⁺ + 4e⁻. Overall: 2H₂O → 2H₂ + O₂. The volume of H₂ collected is double that of O₂. Acidified water (with H₂SO₄) enhances conductivity. Platinum electrodes are used.
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