Question

which of the following would contain the largest number of moles?

1. 5.00 grams of copper (cu)
2. all the answers contain the same number of moles.
3. 5.00 grams of chlorine (cl)
4. 5.00 grams of calcium (ca)
5. 5.00 grams of lithium (li)

Explanation:

To determine which substance contains the largest number of moles, we use the formula for moles: \( n = \frac{m}{M} \), where \( n \) is the number of moles, \( m \) is the mass, and \( M \) is the molar mass. Since the mass (\( m = 5.00 \, \text{g} \)) is the same for all substances, the number of moles is inversely proportional to the molar mass (\( M \)). A smaller molar mass will result in a larger number of moles.

Step 1: Recall the molar masses of each element

• Molar mass of \( \text{Cu} \) (copper): \( M_{\text{Cu}} = 63.55 \, \text{g/mol} \)
• Molar mass of \( \text{Cl} \) (chlorine): \( M_{\text{Cl}} = 35.45 \, \text{g/mol} \)
• Molar mass of \( \text{Ca} \) (calcium): \( M_{\text{Ca}} = 40.08 \, \text{g/mol} \)
• Molar mass of \( \text{Li} \) (lithium): \( M_{\text{Li}} = 6.94 \, \text{g/mol} \)

Step 2: Compare the molar masses

We compare the molar masses: \( 6.94 \, \text{g/mol (Li)} < 35.45 \, \text{g/mol (Cl)} < 40.08 \, \text{g/mol (Ca)} < 63.55 \, \text{g/mol (Cu)} \). Since lithium has the smallest molar mass, it will have the largest number of moles when the mass is constant.

Answer:

1. 5.00 grams of lithium (Li)