Fill in the blank: A mole is defined as the number of carbon atoms in __________ g of pure C-12.

• A. 6.022
• B. 12
• C. 1
• D. 24

Answer: (B)

Verified step by step guidance

1. Recall the definition of a mole: it is the amount of substance that contains exactly Avogadro's number of entities (atoms, molecules, etc.).
2. Avogadro's number is approximately \$6.022 \times 10^{23}\(, which corresponds to the number of atoms in exactly 12 grams of pure carbon-12 (\)^{12}C$).
3. Therefore, the mole is defined as the number of carbon atoms in 12 grams of pure carbon-12.
4. This means that 1 mole of carbon-12 atoms has a mass of exactly 12 grams and contains \$6.022 \times 10^{23}$ atoms.
5. So, the blank in the statement should be filled with the number 12.