Some Basic Concepts of Chemistry

Some Basic Concepts of Chemistry

Question

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

  • 1/103

  • 1/206

  • 2/309

  • 1/412

Answer

D.

1/412

We know the molecular weight of C8H7SO3Na
= 12x8+1x7+32+16x3+23 = 206
we have to find mole per gram of resin
therefore,
1 g of C8H7SO3Na has number of mole
equals fraction numerator weight space of space given space resin over denominator Molecular space weight space of space resin end fraction
=1/206 mol
Taking the reaction,
C8H7SO3Na + Ca2+ → (C6H7SO3)2Ca + 2Na+
therefore, 2 moles of C8H7SO3Na  combines with 1 mol of Ca2+
Thus, 1 mole of C8H7SO3Na will combine with 0.5 mol of Ca2+
Hence, 1/206 mole of C8H7SO3Na will combine with,
 0.5 x (1/206)mol of Ca2+ = 1/412 mol Ca2+

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