How many grams are present in 2.50 \times 10^{23} molecules of CaO?

• A. 56 g
• B. 28 g
• C. 1.4 g
• D. 7.0 g

Answer: (D)

Verified step by step guidance

1. Identify the given quantity: 2.50 \times 10^{23} molecules of CaO.
2. Recall that to convert molecules to grams, you first convert molecules to moles using Avogadro's number, which is 6.022 \times 10^{23} molecules per mole.
3. Calculate the number of moles of CaO by dividing the given number of molecules by Avogadro's number: \(\text{moles} = \frac{2.50 \times 10^{23}}{6.022 \times 10^{23}}\).
4. Determine the molar mass of CaO by adding the atomic masses of calcium (Ca) and oxygen (O). Use the periodic table values: Ca \approx 40.08 \text{ g/mol}, O \approx 16.00 \text{ g/mol}. So, \(\text{molar mass of CaO} = 40.08 + 16.00\) g/mol.
5. Finally, convert moles to grams by multiplying the number of moles by the molar mass: \(\text{mass in grams} = \text{moles} \times \text{molar mass of CaO}\).