Question one should be obvious..
Mass can't be created not destroyed no matter what, so even in a chemical reaction, the answer will remain. The first answer is correct.
Question two
No, because even when water is broken down, there should only be one molecule of oxygen. The fact there is two means it's incorrect.
Question three
Yes. The equation is perfectly balanced on both sides, so it's safe to say the value of mass remains constant.
Answer:

Explanation:
Hello,
In this case, by using the Avogadro's law which allows us to understand the volume-moles behavior as a directly proportional relationship:

We can compute the volume of 34.3 g of argon by representing it in mole as shown below:

Thus, we find:

Best regards.
The negative ion reactions that consist of the formation of carbon dioxide in the atmosphere is generally an exothermic reaction. By definition, an exothermic reaction takes place when the chemical process eventually releases heat as its by-product. It is in contrast in endothermic process wherein heat is absorbed.