Which statement about the mole is correct?
AOne mole always refers only to molecules.
BOne mole of $Na^+$ means $6.022 \times 10^{23}$ sodium ions.
COne mole of helium contains $6.022 \times 10^{23}$ molecules of $He_2$.
DOne mole is defined as the mass of one particle in grams.
Answer & Solution
Correct answer: B. One mole of $Na^+$ means $6.022 \times 10^{23}$ sodium ions.
The chapter states that a mole may refer to atoms, molecules, ions, or electrons. Therefore, one mole of $Na^+$ means Avogadro's number of sodium ions. Option A is too restrictive, C is wrong because helium is monoatomic, and D is not the definition of a mole.