Weight of reactants is not always equal to weight of products.

Answer

### Step-by-Step Solution:

1. **Understanding the Statement**: The statement claims that the weight of reactants is not always equal to the weight of products. We need to determine if this statement is true or false.

2. **Applying the Law of Conservation of Mass**: According to the law of conservation of mass, the total mass (or weight) of the reactants in a chemical reaction must equal the total mass (or weight) of the products. This means that in a closed system, matter cannot be created or destroyed.

3. **Evaluating the Statement**: Since the law of conservation of mass states that the weight of reactants must equal the weight of products, the statement is false.

4. **Example to Support the Explanation**: To illustrate this, let’s consider the formation of water (H2O) from hydrogen (H2) and oxygen (O2):
- The balanced chemical equation for this reaction is:
\[ 2H_2 + O_2 \rightarrow 2H_2O \]
- In this reaction, we have:
- 2 molecules of hydrogen (H2) contribute a weight of \(2 \times 2 = 4 \text{ grams}\) (since each H atom weighs 1 gram).
- 1 molecule of oxygen (O2) contributes a weight of \(1 \times 16 = 16 \text{ grams}\) (since each O atom weighs 16 grams).
- Therefore, the total weight of the reactants is:
\[ 4 \text{ grams (H2)} + 16 \text{ grams (O2)} = 20 \text{ grams} \]
- For the products (water), we have:
- 2 molecules of water (H2O) contribute a weight of \(2 \times (2 + 16) = 36 \text{ grams}\) (2 grams from hydrogen and 16 grams from oxygen).
- Thus, the total weight of the products is also 20 grams.

5. **Conclusion**: Since the total weight of the reactants (20 grams) is equal to the total weight of the products (20 grams), this supports the law of conservation of mass. Therefore, the original statement is false.