Answer:
The answer is B. Place a 2 in front of the HCl
Ba + 2HCl → BaCl2 + H2
Explanation:
According to the law of the conservation of matter, no atom can create or destroy in a chemical reaction. Then the number of atoms that are present in the reagents has to be equal to the number of atoms present in the products. Therefore, if the number of atoms is not equal, the equation must be balanced.
First you must determine the amount of atoms of each element present in both reagents and products. For that you must observe the subscripts next to each atom. In this case:
Reagents (left side of the reaction):
- H: 1 atom
- Cl: 1 atom
- Ba: 1 atom
Products (right side of the equation):
- Ba: 1 atom
- Cl: 2 atoms
- H: 2 atoms
You can see that there aren't the same number of atoms of Cl and H in reagents and products. So you have to balance the chemical reaction.
In a chemical equation, you can change coefficients, but you should never alter the subscripts. And it is always preferable not to start balancing with H. In this case, you start balancing the chlorine. For that you add the coefficient 2 to the HCl molecule to the right of the equation to balance it with the 2 Cl atoms to the left of the equation (present in BaCl2). So:
Ba + 2HCl → BaCl2 + H2
Now you must determine the amount of atoms of each element present in both reagents and products again to see if the reaction is balanced or not. Remember that by multiplying the coefficient by the subindice of each atom, you get the amount of that atom.
Reagents (left side of the reaction):
- H: 2 atom
- Cl: 2 atom
- Ba: 1 atom
Products (right side of the equation):
- Ba: 1 atom
- Cl: 2 atoms
- H: 2 atoms
You can see that you have the same amount of each atom on each side of the reaction. This means that the reaction is balanced.
So the answer is
Ba + 2HCl → BaCl2 + H2
and you placed a 2 in front of the HCL
