Acids, Bases and Salts

Which of the following statement is not correct ?

Which of the following is(are) true when HC1 (g) is passed through water ?
(i) It does not ionise in the solution as it is a covalent compound.
(ii) It ionises in the solution.
(iii) It gives both hydrogen and hydroxyl ion in the solution.
(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.

Which of the following statements is true for acids ?

Which of the following substance will not give carbon dioxide on treatment with dilute acid ?

Which of the following is acidic in nature ?

Which of the following is used for dissolution of gold ?