QuestionMay 13, 2025

4. How many formula units are contained in 0.67 g CaO?

4. How many formula units are contained in 0.67 g CaO?
4. How many formula units are contained in 0.67 g CaO?

Solution
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Answer

Approximately 7.20 \times 10^{21} formula units of CaO. Explanation 1. Calculate Molar Mass of CaO The molar mass of calcium (Ca) is 40.08 g/mol and oxygen (O) is 16.00 g/mol. Thus, the molar mass of CaO is 40.08 + 16.00 = 56.08 g/mol. 2. Convert Grams to Moles Use the formula: **moles = \frac{\text{mass}}{\text{molar mass}}**. For 0.67 g of CaO, moles = \frac{0.67}{56.08}. 3. Calculate Number of Formula Units Use Avogadro's number: **number of units = \text{moles} \times 6.022 \times 10^{23}**. Multiply the moles from Step 2 by Avogadro's number.

Explanation

1. Calculate Molar Mass of CaO<br /> The molar mass of calcium (Ca) is 40.08 g/mol and oxygen (O) is 16.00 g/mol. Thus, the molar mass of CaO is $40.08 + 16.00 = 56.08$ g/mol.<br /><br />2. Convert Grams to Moles<br /> Use the formula: **moles = \frac{\text{mass}}{\text{molar mass}}**. For 0.67 g of CaO, moles = $\frac{0.67}{56.08}$.<br /><br />3. Calculate Number of Formula Units<br /> Use Avogadro's number: **number of units = \text{moles} \times 6.022 \times 10^{23}**. Multiply the moles from Step 2 by Avogadro's number.
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