The Avogadro constant is:
6.022 × 1023
Understanding the Avogadro Constant
The Avogadro constant, also known as Avogadro's number, is a fundamental constant in chemistry and physics. It represents the number of constituent particles (such as atoms, molecules, ions, or electrons) that are contained in one mole of a given substance. The concept is named after the Italian scientist Amedeo Avogadro.
Value of the Avogadro Constant
The internationally accepted value for the Avogadro constant is based on the redefined SI base units, where the mole is defined by fixing the numerical value of the Avogadro constant.
Its value is defined as exactly:
\(N_A = 6.02214076 \times 10^{23} \text{ mol}^{-1}\)
For most practical purposes, including standard calculations in chemistry, a rounded value is commonly used.
The widely used approximate value of the Avogadro constant is \(6.022 \times 10^{23}\).
Analyzing the Options
Let's look at the given options for the value of the Avogadro constant:
| Option Number | Given Value | Comparison with \(6.022 \times 10^{23}\) |
|---|---|---|
| 1 | \(3.022 \times 10^{23}\) | Incorrect. The mantissa (3.022) is different. |
| 2 | \(6.22 \times 10^{23}\) | Incorrect. The mantissa (6.22) is different. |
| 3 | \(6.022 \times 10^{34}\) | Incorrect. The exponent (34) is different from 23. |
| 4 | \(6.022 \times 10^{23}\) | Correct. This matches the commonly used approximate value. |
Comparing the options with the standard value of the Avogadro constant, \(6.022 \times 10^{23}\), we see that only Option 4 matches this value.
Significance in Chemistry: The Mole Concept
The Avogadro constant is crucial for understanding the mole concept. A mole of any substance contains the Avogadro number of elementary entities (atoms, molecules, etc.). This allows us to relate the microscopic world of atoms and molecules to the macroscopic world of measurable quantities like mass and volume.
- One mole of carbon-12 atoms has a mass of exactly 12 grams and contains approximately \(6.022 \times 10^{23}\) atoms.
- One mole of water molecules has a mass approximately equal to its molar mass (18.015 g/mol) and contains approximately \(6.022 \times 10^{23}\) water molecules.
Conclusion
Based on the definition and the accepted value of the Avogadro constant, the value \(6.022 \times 10^{23}\) is the correct one among the given options.
Revision Table: Key Facts about Avogadro Constant
| Term | Definition/Value |
|---|---|
| Avogadro Constant (\(N_A\)) | Number of particles in one mole of a substance. |
| Commonly Used Value | \(6.022 \times 10^{23}\) |
| SI Unit | \(\text{mol}^{-1}\) |
| Related Concept | Mole |
Additional Information: Mole and Molar Mass
The Avogadro constant links the number of particles to the amount of substance (mole).
- Mole (mol): The SI unit for the amount of substance. One mole contains exactly \(6.02214076 \times 10^{23}\) elementary entities.
- Molar Mass (M): The mass of one mole of a substance, usually expressed in grams per mole (g/mol). It is numerically equal to the atomic or molecular mass in atomic mass units (u). For example, the atomic mass of Oxygen is approximately 16 u, so its molar mass is approximately 16 g/mol. This means 16 grams of Oxygen contains approximately \(6.022 \times 10^{23}\) Oxygen atoms.
The relationship between mass (\(m\)), molar mass (\(M\)), and amount of substance (\(n\)) is given by \(n = \frac{m}{M}\). The number of particles (\(N\)) can then be found using \(N = n \times N_A = \frac{m}{M} \times N_A\).
Important Questions from Structure of Atom
According to J.J. Thomson model of atom, positive charge is - Idenfity
Ions differ from their corresponding atoms in
- How many moles of He atoms are present in its 20 u mass ?
Which of the following electron transition in hydrogen atom will require largest amount of energy?
A species having 8 electrons in the third shell is very reactive while the other species having 8 electrons in the third shell is very inactive they are :
