The molecular formula of a commercial resin used for exchanging ions in water softening is C8H7SO3Na (molecular weight 206). What would be the maximum uptake of Ca2+ ions by the resin when expressed in mole per gram resin?

The molecular weight of resin is 206 g/mol. 1 g of resin corresponds to 1/206 moles.
The resin exchanges Na+ ions for Ca2+ ions. The reaction can be represented as:
2C8H7SO3Na + Ca2+ <--> (C8H7SO3)2Ca + 2Na+
From the stoichiometry, 2 moles of resin react with 1 mole of Ca2+. Therefore, 1 mole of resin reacts with 0.5 moles of Ca2+.
Since 1 g of resin corresponds to 1/206 moles, the maximum uptake of Ca2+ ions by the resin would be (1/206) * 0.5 moles/g = 0.002427 moles/g.
This is approximately equal to 1/206 * 0.5 = 0.002427 mol/g. None of the provided options match this calculated value. There might be an error in the provided options or the question itself. The closest option is 1/206 = 0.004854 mol/g. If we assume the question meant to ask about the moles of resin in 1 gram, then the answer would be 1/206 mol/g ≈ 0.00485 mol/g. However, given the reaction stoichiometry, this value should be halved to account for the Ca2+ uptake. Therefore, a correct answer not present in the options is approximately 0.00243 moles/g.