Any substance which yields a hydrogen ion when placed in a water solution is call

a. acid
b. indicator
c. base
d. salt

it is A Acid

Explanation : Any substance that yields a hydrogen ion when placed in a water solution is called an acid. According to Arrhenius theory of Acids and Bases, Acids are those substances which on dissociation in solution generates ions. Whereas a Base is a substance that dissociates in the solution to produce ions.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.

yes the answer is total mass in unchanged   : )