Question

Which of the following pair of solution (aq.) contain
isotonic solution at same temperature? (Assume 100%
jonisation of electrolytes)

0.1 M NaCl and 0.2 M CaCl2
0.1 M NaCl and 0.3 M AlCl3
0.3 M NaCl and 0.1 M AICI3
0.3 M NaCl and 0.2 M CaCl2​

Answer 1

Answer:

Ist option is the correct..............

Answer 2

Answer:

The correct answer is found to be option (d) 0.3M NaCl and 0.2M $CaCl_2$.

Explanation:

Isotonic solutions are the ones which have the same pressure.

We know that the expression for the osmotic pressure is given by the following equation:

Osmotic pressure (П) = iCRT

where i represents the i factor or in this case, the number of atoms in the molecule,

and C represents Molarity.

Now, using this expression to find the pressure for the given options, we get:

(i) 0.1M NaCl and 0.2M $CaCl_2$:

For NaCl: П=0.2RT and for $CaCl_2$:  П=0.6RT

(ii) 0.1 M NaCl and 0.3 M $AlCl_3$:

For NaCl: П=0.2RT and for $AlCl_3$:  П=1.2RT

(iii) 0.3 M NaCl and 0.1 M $AlCl_3$:

For NaCl: П=0.6RT and for $AlCl_3$:  П=0.4RT

(iv) 0.3M NaCl and 0.2M $AlCl_3$:

For NaCl: П=0.6RT and for $AlCl_3$:  П=0.6RT

Thus, option (iv) is the correct answer.

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