Consider the following laws
(I) Law of conservation of mass
(II) Law of definite proportions
(III) Law of multiple proportions
Which of the above govern (s) the quantitative aspects of chemical changes?

Options

A. Only (I)
B. (II) and (III)
C. (I) and (II)
D. All of these

Explanation

To determine which of the laws govern the quantitative aspects of chemical changes, we will analyze each law step by step.

### Step 1: Understand the Law of Conservation of Mass
The Law of Conservation of Mass states that in a chemical reaction, the mass of the reactants is equal to the mass of the products. This means that matter cannot be created or destroyed in a chemical reaction.

**Hint:** Think about how mass is measured and conserved during reactions.

### Step 2: Analyze the Law of Definite Proportions
The Law of Definite Proportions states that a chemical compound always contains its component elements in fixed ratio by mass, regardless of the source or method of preparation. For example, water (H₂O) always consists of hydrogen and oxygen in a 2:1 ratio.

**Hint:** Consider how the fixed ratios relate to the quantities of elements in compounds.

### Step 3: Examine the Law of Multiple Proportions
The Law of Multiple Proportions states that when two elements can combine in different ways to form different compounds, the ratios of the masses of one element that combine with a fixed mass of the other element are simple whole numbers. For example, carbon and oxygen can form CO and CO₂, where the ratio of oxygen in these compounds is a simple ratio.

**Hint:** Reflect on how the ratios of different compounds formed by the same elements indicate quantitative relationships.

### Step 4: Conclusion
All three laws—Law of Conservation of Mass, Law of Definite Proportions, and Law of Multiple Proportions—govern the quantitative aspects of chemical changes. They all involve measurements and ratios that are fundamental to understanding chemical reactions.

**Final Answer:** All of the above laws govern the quantitative aspects of chemical changes.