In 2Na + Cl₂ → 2NaCl, sodium is oxidized (Na → Na⁺ + e⁻) and chlorine is reduced (Cl₂ + 2e⁻ → 2Cl⁻). It involves change in oxidation states. Options A and B are double displacement (no change in oxidation states). Option D is decomposition with no change in oxidation states (Ca: +2 remains +2). Redox reactions involve simultaneous oxidation and reduction.
Explanation:
Calgon is the trade name for sodium hexametaphosphate (Na6P6O18). It is used to soften hard water because the hexametaphosphate ion binds (chelates) with calcium and magnesium ions in the water, forming a soluble complex. This prevents the metal ions from interfering with soap lathering.
Explanation:
Neutralization is the reaction of an acid and a base to form salt and water. HCl (acid) + NaOH (base) → NaCl (salt) + H₂O. Option A is combination; C is decomposition; D is displacement.
Explanation:
Atomic number 11 is sodium (Na). The electron shells fill as 2 in K, 8 in L, and the remaining 1 in M. Thus configuration is 2,8,1. It belongs to Group 1 (alkali metals) and Period 3. The configuration determines its valency (1) and reactivity.
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