Equal volumes of different gases at any definite temperature and pressure have.

Options

A. equal atoms
B. equal masses
C. equal densities
D. equal molecules

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the relationship between equal volumes of different gases at a constant temperature and pressure.

2. **Introducing Avogadro's Law**: According to Avogadro's Law, at the same temperature and pressure, equal volumes of different gases contain an equal number of molecules. This means that if we have two different gases occupying the same volume under the same conditions, they will have the same number of molecules.

3. **Applying the Ideal Gas Equation**: The Ideal Gas Law is given by the equation \( PV = nRT \), where:
- \( P \) = pressure
- \( V \) = volume
- \( n \) = number of moles
- \( R \) = universal gas constant
- \( T \) = temperature

Since we are considering equal volumes of gases at constant temperature and pressure, we can rearrange the equation to show that the number of moles (\( n \)) is directly proportional to the volume (\( V \)) when \( P \) and \( T \) are constant.

4. **Conclusion**: Therefore, if the volumes of the gases are equal and the conditions of temperature and pressure are constant, the number of molecules in those gases will also be equal.

5. **Final Answer**: Equal volumes of different gases at any definite temperature and pressure have equal numbers of molecules.

---