Solved: CHEMISTRY Question for NEET | Sushrut

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NEET CHEMISTRYMedium

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8H_7SO_3Na$ (Mol. Wt. 206). The maximum uptake of $Ca^{2+}$ ions by the resin when expressed in mole per gram resin is based on the reaction: $2C_8H_7SO_3Na + Ca^{2+} \rightarrow (C_8H_7SO_3)_2Ca + 2Na^+$

A

1/103

B

1/206

C

2/309

D

1/412

Step-by-Step Solution

Analyze Stoichiometry: From the balanced chemical equation, 2 moles of the resin ( $C_8H_7SO_3Na$ ) react with 1 mole of calcium ions ( $Ca^{2+}$ ) to maintain charge neutrality (replacing two $+1$ ions with one $+2$ ion).
Calculate Mass of Resin:

Molar Mass of Resin = $206 \text{ g mol}^{-1}$ .
Mass of 2 moles of Resin = $2 \times 206 \text{ g} = 412 \text{ g}$ .

Calculate Uptake:

The uptake is defined as the moles of $Ca^{2+}$ absorbed per gram of resin.
Uptake = $\frac{\text{Moles of } Ca^{2+}}{\text{Mass of Resin}}$
Uptake = $\frac{1 \text{ mol}}{412 \text{ g}}$
Uptake = $\frac{1}{412} \text{ mol g}^{-1}$ .

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