To balance the chemical equation [tex]\( Zn + HCl \rightarrow ZnCl_2 + H_2 \)[/tex], let's follow a step-by-step approach:
1. Examine the reactants and products in their unbalanced form:
- Left side (reactants): [tex]\(Zn\)[/tex] and [tex]\(HCl\)[/tex]
- Right side (products): [tex]\(ZnCl_2\)[/tex] and [tex]\(H_2\)[/tex]
2. Count the number of atoms for each element on both sides:
- For Zinc ([tex]\(Zn\)[/tex]):
- Left: 1 [tex]\(Zn\)[/tex]
- Right: 1 [tex]\(Zn\)[/tex]
- For Hydrogen ([tex]\(H\)[/tex]):
- Left: 1 [tex]\(H\)[/tex] from [tex]\(HCl\)[/tex]
- Right: 2 [tex]\(H\)[/tex] in [tex]\(H_2\)[/tex]
- For Chlorine ([tex]\(Cl\)[/tex]):
- Left: 1 [tex]\(Cl\)[/tex] from [tex]\(HCl\)[/tex]
- Right: 2 [tex]\(Cl\)[/tex] in [tex]\(ZnCl_2\)[/tex]
3. Balance the chlorine atoms first:
- On the left side, there's 1 [tex]\(Cl\)[/tex] in [tex]\(HCl\)[/tex].
- On the right side, there are 2 [tex]\(Cl\)[/tex] in [tex]\(ZnCl_2\)[/tex].
To balance [tex]\(Cl\)[/tex], place a coefficient of 2 in front of [tex]\(HCl\)[/tex] on the left side:
[tex]\( Zn + 2 HCl \rightarrow ZnCl_2 + H_2 \)[/tex]
4. Verify the hydrogen atoms are balanced:
- Left side: 2 [tex]\(H\)[/tex] from [tex]\(2 HCl\)[/tex]
- Right side: 2 [tex]\(H\)[/tex] from [tex]\(H_2\)[/tex]
5. Check all elements are balanced:
- Zinc ([tex]\(Zn\)[/tex]): 1 atom on both sides.
- Hydrogen ([tex]\(H\)[/tex]): 2 atoms on both sides.
- Chlorine ([tex]\(Cl\)[/tex]): 2 atoms on both sides.
Everything is balanced with the coefficient of 2 in front of [tex]\(HCl\)[/tex].
So, the number that should be placed in front of [tex]\(HCl\)[/tex] to balance this chemical equation is:
Answer: A. 2
