1. **Problem:** How many atoms are present in 2.76 mol of Cassiterite SnO2? 2. **Understanding the problem:** Cassiterite has the formula SnO2, meaning each molecule contains 1 atom of Sn and 2 atoms of O, totaling 3 atoms per formula unit. 3. **Formula used:** Total atoms = number of moles × Avogadro's number × atoms per formula unit 4. **Known values:** - Number of moles, $n = 2.76$ mol - Avogadro's number, $N_A = 6.022 \times 10^{23}$ atoms/mol - Atoms per formula unit = 3 (1 Sn + 2 O) 5. **Calculation:** $$\text{Total atoms} = 2.76 \times 6.022 \times 10^{23} \times 3$$ 6. Multiply step-by-step: - $2.76 \times 3 = 8.28$ - $8.28 \times 6.022 \times 10^{23} = 4.986 \times 10^{24}$ atoms (approx.) 7. **Answer:** Approximately $4.98 \times 10^{24}$ atoms are present. **Correct choice:** D. 4.98 x 10^24 atoms