Which of the following is not a balanced chemical equation?

Options

A. `H_2 + CuO to Cu + H_(2)O`
B. `Zn+ 2AgNO_3 to Zn(NO_3) _2+ 2Ag`
C. `Mg+ 2HCl to MgCl_2 + H_2`
D. `4Al + 2HCl to 2AlCl_3 + 4H_2`

Explanation

To determine which of the following equations is not a balanced chemical equation, we need to analyze each equation and check if the number of atoms of each element is the same on both sides of the equation.

### Step-by-Step Solution:

1. **Understand the Definition of a Balanced Chemical Equation**:
- A balanced chemical equation has an equal number of atoms of each element on both the reactant side (left) and the product side (right).

2. **Examine Each Option**:
- **Option A**: Check if the equation is balanced.
- If it has equal numbers of each type of atom on both sides, it is balanced.
- **Option B**: Check if the equation is balanced.
- Again, ensure that the number of atoms of each element is the same on both sides.
- **Option C**: Check if the equation is balanced.
- Verify the count of atoms for each element.
- **Option D**: Check if the equation is balanced.
- Count the atoms on both sides.

3. **Identify the Unbalanced Equation**:
- After checking each option, identify which equation does not have the same number of atoms for at least one element on both sides.

4. **Conclusion**:
- The equation that does not have equal numbers of atoms for each element is the unbalanced equation.

### Final Answer:
- The equation in **Option D** is not a balanced chemical equation.