Question

PLZ EXPLAIN AND ANS


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 resin when
expressed in mole per gram resin?
a)
2/309
b)
1/412
c)
1/103
d)
1/206

Answer 1

Answer:

1/412

Explanation:

The maximum uptake of Ca

+2

 ion in grams per resin is:

2×206g

or

2mol

2C

8

​

H

7

​

SO

3

​

Na

​

​

​

+

1mol

Ca

2+

​

→(C

8

​

H

7

​

SO

3

​

)

2

​

Ca+2Na

+

 

From the above reaction, it can be observed that 2 moles of resin take up 1 mole of Ca.

i.e 206 x 2 g = 412 g of resin takes up 1 mole of Ca.

Number of moles of Ca

2+

 removed by one gram resin =

412

1

​

mol

Hence, option B is correct.

Answer 2

Answer:

Correct option is

B.. 1/412

Explanation:

The molecular weight of resin is 206 g/mol.

1 g of resin corresponds to  1/206moles.

1 mole of calcium ions will displace 2 moles of sodium ions from resin.

1 mole of resin contains 1 mole of sodium ions and can uptake upto 0.5 moles of calcium ions.

Hence, 1 g of resin will uptake  

1/206

×0.5=  1/412 moles of calcium ions.