If 1 mole of NaCl and 1 mole AlCl3 is added to the water. If degree of dissociation of NaCl is 90% and degree of dissociation of AlCl3 is 80%. What is the Van’t Hoff factor is?
A
1.3
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B
3.95
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C
2.65
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D
4.2
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Solution
The correct option is C 2.65 For calculating Van’t Hoff factor 1 we have to know the final number of. particles in the solution.
As the degree of dissociation of salts are given we can easily find the no. of particles.
As same way we did in the last question NaCl→Na++Cl−1001−0.90.90.9(0.1) AlCl3→Al+3cl−1001−0.80.83×0.8(0.2)2.4
We have takne 1 mole of NaCl and AlCl3 each.
0.9 moles of NaCl dissociated giving 0.9 moles of Na+ and Cl− each and learning 0.1 mole of undissociated NaCl is the solution. 0.8 moles of AlCl3 dissociated gives 0.8 moles of Al3 + and 2.4 moles of Cl− ions and learning 0.2 moles of AlCl3 undissociated.
So intial no. of particles taken = 1+1=2↓↓(NaCl)(Alcl3)
Final no. of all particles = (0.1 + 0.9 + 0.9) + (0.2 + 0.8 + 2.4)
= 1.9 + 3.4 = 5.3
Van’t Hoff factor 5.32=2.65