if 20ml of0.4n naoh solution completly neutralises 40ml of a dibasic acid .the molarity of the acid solution is?

Dear student
Please find the similar link to your asked query:

https://www.meritnation.com/ask-answer/question/0-45-g-of-a-dibasic-acid-is-completely-neutralised-with-100/some-basic-concepts-of-chemistry/9098369

[Note : in your question molarity of the acid solution is required. So when the no.of moles of the dibasic acid are obtained , then we know that $Molarity =\frac{no.of moles of dibasic acid}{Volume of solution in ltr}$
Using this formula the Molarity of the acid can be calculated.]

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