The relative atomic mass of sodium is 23. Which of the following statements is not correct about sodium?

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Atomic mass of sodium is 23 u.

Atomic mass of sodium is $3.82 \times 10^{- 26} kg$

Molar mass of sodium is $23 g {mol}^{- 1}$

The number of atoms in 24 kg of sodium is $6.022 \times 10^{23}$

answer is D.

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Detailed Solution

Explanation:

1. Atomic mass of sodium is 23 u: This is correct. The relative atomic mass of sodium is 23 atomic mass units (u), which is defined as 1/12 the mass of a carbon-12 atom.
2. Atomic mass of sodium is 3.82×10⁻²⁶ kg: This is also correct. The atomic mass in kilograms can be calculated as:
23 u × 1.6605×10⁻²⁷ kg/u = 3.82×10⁻²⁶ kg.
3. Molar mass of sodium is 23 g/mol: This is correct. Molar mass represents the mass of 1 mole of sodium atoms, which equals 23 g/mol.
4. The number of atoms in 24 kg of sodium is 6.022×10²³: This is incorrect. The number of atoms can be calculated as follows:
- Number of moles:
  Mass of sodium / Molar mass = 24 kg / 0.023 kg/mol = 1043.48 mol.
- Number of atoms:
  Number of moles × Avogadro's number = 1043.48 mol × 6.022×10²³ atoms/mol = 6.28×10²⁶ atoms.
The given value (6.022×10²³) corresponds to only 1 mole of sodium, not 24 kg, making this statement incorrect.