# While adding simultaneous equilibria , when is the dissociation constant of both reactions the same?

I have a doubt regarding chemical and ionic equilibrium .In reactions involving simultaneous equilibria , instead of analysing the equilibrium simultaneously we sometimes add/substract both the equilibrium and then find net equilibrium constant and solve it easily .But then we assume that both the reactions have same degree of dissociation (alpha) which is not always true ,Thats why we sometimes get wrong answer while adding the simultaneous equilibria. SO basically how do we get to know when the degree of dissociation of both rexn being added will be same ?

• Adding equilibrium equations has little to do with chemistry, but it is mathematical operation, that may be advantageous at some scenarios. If L1 = P1 and L2=P2, then L1+ L2 = P1 + P2. but there is no assuption of the same dissociation constant. Can you provide more context and particular illustrative examples ? BTW, alpha is not dissociation constant, as it is not a constant at the first place. It is the dissociation degree. – Poutnik Jun 21 at 9:52
• yes sorry its degree of dissociation\ – Raghav Madan Jun 21 at 9:55
• how can i attach images in comments ? – Raghav Madan Jun 21 at 9:57
• Why not to attach them to the question body ? // Using photos/screenshots of text ( especially if handwritten ) instead of typing text itself is highly discouraged. The image text content cannot be indexed nor searched for, cannot be reused nor referred in answers. Additionally, it can be challenge to decipher. Consider copy/pasting or rewriting of the essential parts and using of MathJax for eventual formatting of mathematical/chemical formulas or equations. – Poutnik Jun 21 at 12:31