Question

Thermal stability order of Group 1 hydroxides is:

• A. LiOH $<$ NaOH $<$ KOH $<$ RbOH $<$ CsOH
• B. CsOH $<$ RbOH $<$ KOH $<$ NaOH $<$ LiOH
• C. LiOH $>$ NaOH $>$ KOH $>$ RbOH $>$ CsOH
• D. LiOH = NaOH = KOH = CsOH

Hint:

In Group 1, thermal stability of hydroxides increases down the group due to decreasing cationic charge density and polarization.

Answer 1

The Correct Option is A

The thermal stability of Group 1 hydroxides increases as we move down the group. This is because the size of the alkali metal cation increases down the group, reducing the polarizing power of the cation. As a result, the hydroxide bond becomes more stable and resists decomposition upon heating. Hence, the correct order is: \[ \text{LiOH} > \text{NaOH} > \text{KOH} > \text{RbOH} > \text{CsOH} \]