Which of the following acid remains unaffected on heating ?

Which of following acid remains unaffected on heating ?

Which of following acid remains unaffected on heating?

Which of the following equilibria remains unaffected by a change in pressure (or volume)?

Which of the following will be obtained on heating orthophosphorous acid ?

Which of the following acid will form an (a) Anhydride on heating and (b) Acid amide on strong heating with ammonia?

Which of the following acid will form an (a) Anhydride on heating and (b) Acid amide on strong heating with ammonia?