Chemical equations are balanced to reflect that ________

Options

A. matter can change its state during chemical reactions
B. matter cannot be created or destroyed during chemical reactions
C. heat is an important input in chemical reactions
D. all chemical reactions are always reversible

Answer

To answer the question "Chemical equations are balanced to reflect that ________", we need to understand the principle behind balancing chemical equations.

### Step-by-Step Solution:

1. **Understanding Chemical Reactions**:
- A chemical reaction involves the transformation of reactants into products. During this process, atoms are rearranged but not created or destroyed.

2. **Skeletal Equation**:
- Consider a skeletal equation:
\[ \text{Mg} + \text{O}_2 \rightarrow \text{MgO} \]
- Here, magnesium (Mg) reacts with oxygen (O₂) to form magnesium oxide (MgO).

3. **Identifying Imbalance**:
- In the skeletal equation, the reactant side has 2 oxygen atoms (from O₂) and the product side has only 1 oxygen atom (in MgO). This indicates that the equation is not balanced.

4. **Balancing the Equation**:
- To balance the equation, we need to ensure that the number of atoms for each element is the same on both sides.
- We can achieve this by adjusting the coefficients:
\[ 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \]
- Now, we have 2 magnesium atoms and 2 oxygen atoms on both sides of the equation.

5. **Conservation of Mass**:
- The balanced equation reflects the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass of reactants must equal the total mass of products.

6. **Conclusion**:
- Therefore, chemical equations are balanced to reflect that **matter cannot be created or destroyed during a chemical reaction**.

### Final Answer:
Chemical equations are balanced to reflect that **matter cannot be created or destroyed during a chemical reaction**.