What is the approximate $pH$ value for a solution,if $pH$ paper turns pink when dipped into it?

$(a)$ If we take hydrochloric acid and acetic acid of the same concentration,which one will produce a lower $H^{+}$ ion concentration? Out of the two,which one is a weak acid?
$(b)$ If someone is suffering from acidity,which of the following would you suggest to cure it: vinegar,orange juice,or baking soda solution? Give a reason for your answer.

What are olfactory indicators?

How does the acidity of an acidic aqueous solution change as the concentration of $[H_{3}O^{+}]$ decreases?

What effect does an increase in the concentration of $H^{+}(aq)$ in a solution have on the $pH$ of the solution?

$A$ sulphate salt of a Group $2$ element of the Periodic Table is a white,soft substance,which can be moulded into different shapes by making its dough. When this compound is left in the open for some time,it becomes a hard solid mass and cannot be used for moulding purposes. Identify the sulphate salt and explain why it shows such behavior. Provide the chemical reaction involved.