Answer:
Option B. 2Mg(s) + O2 (g) —> 2MgO (s)
Explanation:
From the question given above,
We were told that:
2 solid Mg atoms bond with O2 gas to produce solid MgO.
This can be represented by an equation as follow:
2Mg(s) + O2 (g) —> MgO (s)
Next, we shall balance the above equation as follow:
2Mg(s) + O2 (g) —> MgO (s)
There are 2 atoms of Mg on the left side and 1 atom on the right side. It can be balance by putting 2 in front of MgO as shown below:
2Mg(s) + O2 (g) —> 2MgO (s)
Now, the equation is balanced.
Answer:
Explanation:
When we react Hydrochlorid Acid with zinc we have the following reaction:
2HCl(aq) + Zn(s) --> ZnCl2(aq) + H2(g)
The hydrogen gas formed is lost to the environment, so we can affirme that in the start we have the mass for all the H, Cl and Zn atoms in the solution, but after the reaction occurs, we have only the mass for the Cl and Zn atoms.
That's why the mass is less than the original.
The law that the student was told is only applied to closed environments.
