What happens when nitric acid is added to an egg shell?

According to the Bronsted-Lowry acid-base theory,the substance which accepts a proton $(H^+)$ from another substance is called ...........

$(a)$ 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.

Write true or false for the following statements:
Care must be taken while mixing concentrated nitric acid or sulphuric acid with water. The water must always be added slowly to the acid with constant stirring.

To protect against tooth decay,we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is:

When a $pH$ paper is dipped in an aqueous solution,it turns blue. What is the approximate $pH$ value of that solution?