Two samples of lead oxide were separately reduced to metallic lead by heating in a current of hydrogen. The weight of lead from one oxide was half the weight of lead obtained from the other oxide. The data illustrate

Options

A. law of reciprocal proportions
B. law of constant proportions
C. law of multiple proportions
D. law of equivalent proportions

Explanation

To solve the problem, we need to analyze the situation described and determine which law of chemical combination is illustrated by the reduction of two samples of lead oxide to metallic lead.

### Step-by-Step Solution:

1. **Understanding the Experiment**:
- We have two samples of lead oxide (PbO).
- Each sample is reduced to metallic lead (Pb) by heating in a current of hydrogen (H₂).

2. **Weight Relationship**:
- The problem states that the weight of lead obtained from one oxide sample is half the weight of lead obtained from the other oxide sample.
- Let’s denote the weight of lead from the first sample as \( m_1 \) and from the second sample as \( m_2 \). According to the problem, \( m_1 = \frac{1}{2} m_2 \).

3. **Implications of Weight Difference**:
- This indicates that the two samples of lead oxide have different compositions or different amounts of lead in them.
- The reduction process shows that the mass of lead produced is dependent on the composition of the lead oxide.

4. **Identifying the Applicable Law**:
- **Law of Constant Proportion**: This law states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the source or method of preparation.
- In this case, even though the weights of lead obtained from the two different samples are different, the lead oxide still contains lead in a consistent ratio relative to its composition.
- **Law of Multiple Proportions**: This law applies when two elements can combine in different ratios to form different compounds. However, in this scenario, we are only dealing with lead oxide and its reduction to lead, not different compounds formed by the same elements.
- **Law of Reciprocal Proportions**: This law is not applicable here as we are not comparing two different elements combining with a fixed mass of a third element.
- **Law of Equivalent Proportions**: This is similar to the law of reciprocal proportions and does not apply here.

5. **Conclusion**:
- The situation illustrates the **Law of Constant Proportion** because both samples of lead oxide yield lead in a consistent manner based on their respective compositions, even though the weights differ.

### Final Answer:
The data illustrate the **Law of Constant Proportion**.