Exams › JEE Advanced › Chemistry
Correct answer: 4
Hemimorphite is a zinc silicate mineral. Its formula is Zn₄(OH)₂ Si₄ O₁₄ (sometimes written as Zn₄(Si₂O₇)(OH)₂ * H2O after factoring). Charge balance in Znₓ(OH)₂ Si₄ O₁₄: each Zn²+ contributes +2x. OH(-) contributes -2. Si₄O₁₄: Si is +4 each, O is -2 each. Charge from Si₄O₁₄ = 4*(+4) + 14*(-2) = 16 - 28 = -12. Total charge = 2x + (-2) + (-12) = 0. 2x - 14 = 0 => x = 7. Hmm that gives 7, not an option. Let me try Si₄O₁₁ for the silicate group. Or reconsider: in Znₓ(OH)₂Si₄O₁₁: 2x - 2 + 4*4 + 11*(-2) = 0 => 2x-2+16-22=0 => 2x-8=0 => x=4. The formula might be Znₓ(OH)₂ Si₄ O₁₁ not O₁₄. But the question states O₁₄. Let me try: if the formula is meant as Znₓ(OH)₂(Si₂O₇)₂: Si₂O₇ charge = 2*4+7*(-2) = 8-14 = -6. Two groups: -12. Plus (OH)₂: -2. Total anion charge = -14. Cation charge needed: 2x = 14 => x=7. Still 7. Alternatively, the correct hemimorphite formula is Zn₄[Si₂O₇](OH)₂*H2O = Zn₄Si₂O₇(OH)₂*H2O. If we expand: Zn₄(OH)₂Si₂O₇: charge: +8 - 2 + charge(Si₂O₇). Si₂O₇^(6-): charge = 2*4+7*(-2) = 8-14 = -6. Total: 8-2-6=0. Works with x=4 and Si₂O₇ not Si₄O₁₄. The formula Si₄O₁₄ = (Si₂O₇)₂ would require x=7 but actual hemimorphite has x=4 with Si₂O₇. The question likely has a typo but the standard answer for hemimorphite x = 4.