Which combinations can form buffer solutions? [closed]








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I have a simple questions that I can´t solve . The answer is B though I really dont understand why since all of them have weak acid and a strong base


[![buffer soltuion](https://i.stack.imgur.com/TFl23.png)](https://i.stack.imgur.com/TFl23.png)




In the second option both the acid and base neutralise each other and that leaves out onlysalt (CH3 COONa). But in first and the third case the weak acid and its conjugate is present in appreciable quantity and hence they will show properties of buffer solution. 


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