MHT CET202521 Apr 2025Evening ShiftChemistryIonic EquilibriumActual
A monobasic weak acid dissociates to 1.2 % in its 0.01 M solution at 298 K . Calculate dissociation constant of it.
Options
- A1.04 10⁻⁸
- B1.44 10⁻⁶
- C1.30 10⁻⁶
- D1.18 10⁻⁵
Correct answer
B. 1.44 10⁻⁶
Step-by-step solution
The dissociation constant K_a for a monobasic weak acid is determined from the initial concentration C = 0.01 M and percentage dissociation of 1.2 % . The degree of dissociation is = 1.2/100 = 0.012 . For the equilibrium HA H ^+ + A ^- , the dissociation constant is defined as K_a = [ H ^+][ A ^-]/[ HA ] . Substituting the equilibrium concentrations [ H ^+] = C , [ A ^-] = C , and [ HA ] = C(1- ) yields K_a = C ^2/(1- ) . Since = 0.012 1 , the approximation 1- 1 applies, giving K_a C ^2 . Substituting values: K_a =