JEE Main2015Chemistrys Block ElementsActual
The correct order of thermal stability of hydroxides is
Options
- AM g OH 2 < S r OH 2 < C a OH 2 < B a OH 2
- BM g O H 2 < C a O H 2 < S r O H 2 < B a O H 2
- CB a O H 2 < S r O H 2 < C a O H 2 < M g O H 2
- DB a O H 2 < C a O H 2 < S r O H 2 < M g O H 2
Correct answer
B. M g O H 2 < C a O H 2 < S r O H 2 < B a O H 2
Step-by-step solution
M g OH 2 < C a O H 2 < S r O H 2 < B a O H 2 Thermal stability increases down the group due to the decrease in the charge density of the metal cation. All group 2 metal ions have the same charge (2+) but the smaller ones at the top of the group have it all packed into a smaller space, so they polarise the O-H bond more (pull electrons towards the oxygen). This means the O-H bond is already partly broken, so it requires less heat to break fully. As you go down the group, the O-H is less polarised by the