We should star by checking the equation from right.
First we check how many Zn r there in left hand side. Which is 1. Let us check how many Znr there in right hand side, there is 1.So Zn is balanced, and don't worry about Znplus2 on right hand side it is just the ions not how many zinc r there.
Now let us check how many I are there left hand side. Which is 2. Now how many I are there in right hand side? Only 1.
Answer: A molecule of hydrochloric acid, for example, is composed of a hydrogen atom and a chlorine atom. When these molecules dissolve into water, they separate into a positively charged hydrogen ion and a negatively charged chlorine ion. ... Only some of the molecules of weak acids disassociate when added to water.