CBSE Class 11-science Answered
One mole of anhydrous MgCl2 dissolves in water and librates 25 cal/mol of heat. ?Hhydration of MgCl2 = –30 cal/mol. Heat of dissolution of MgCl2.7H2O(s) is :-
(1)
+5 cal/mol
(2)
–5 cal/mol
(3)
55 cal/mol
(4)
–55 cal/mol
Asked by Atulcaald | 25 May, 2018, 00:24: AM
Option (1) is correct.
Heat of dissolution is + 5 cal/mol.
Solution:
![Given colon
Heat space liberated space when space MgCl subscript 2 space dissolve space in space water space equals space 25 space cal divided by mol
Heat space of space ionisation space equals space 25 space cal divided by mol
Heat space of space hydration space equals space minus 30 space cal divided by mol
We space have comma space space
Heat space of space solution space equals space Heat space of space ionisation space plus space Heat space of space hydration space
space space space space space space space space space space space space space space space space space space space space space space space space space equals space 25 plus left parenthesis negative 30 right parenthesis
space space space space space space space space space space space space space space space space space space space space space space space space space space equals space left parenthesis negative 5 right parenthesis space cal divided by mol
As space Heat space of space ionisation space greater than space bold space Heat space of space hydration space
therefore space Heat space of space solution space equals space plus space 5 space cal divided by mol
It space is space endothermic space dissolution.
space](https://images.topperlearning.com/topper/tinymce/cache/063fd5694b758bf46d9d1d6d9f32af2b.png)
Answered by Varsha | 25 May, 2018, 11:31: AM
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