Answer:
Here's what I get.
Explanation:
Mg + 2HCl ⟶ MgCl₂ + H₂
According to the Law of Conservation of Mass, the total mass of the products must equal the total mass of the reactants.
However, one of the products is a gas, hydrogen. The gas escapes into the atmosphere, so you will not be weighing it at the end of the reaction.
The mass of the test tube and contents after the reaction will be less than before the reaction.
However, that doesn't violate the Law of Conservation of Mass. You just didn't measure the mass of all the products.
Hydrogen Peroxide slowly decomposing into water and oxygen increases the entropy of the universe. Any reaction of a system always increases the degree of the orderliness of the universe. Decomposition is one of the best examples of increasing the entropy. This is when substance is broken down further to elements or other compounds.

Where v is the volume(in L) and t is the temperature(in °K)
