How many moles are in 30 g of salt, given that the chemical formula for salt is NaCl, with the molar mass of Na being 23 g/mol and that of Cl being 35.5 g/mol?
The Correct Answer and Explanation is:
To calculate the number of moles in 30 grams of salt (NaCl), we need to use the following formula for calculating moles:
[
\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}
]
Where:
- Mass is the given amount of salt (30 g),
- Molar Mass is the molar mass of NaCl.
Step 1: Determine the Molar Mass of NaCl
The molar mass of sodium chloride (NaCl) is the sum of the molar masses of sodium (Na) and chlorine (Cl).
- The molar mass of sodium (Na) is 23 g/mol.
- The molar mass of chlorine (Cl) is 35.5 g/mol.
Therefore, the molar mass of NaCl is:
[
\text{Molar Mass of NaCl} = 23 \, \text{g/mol (Na)} + 35.5 \, \text{g/mol (Cl)} = 58.5 \, \text{g/mol}
]
Step 2: Calculate the Number of Moles
Now, we can calculate the number of moles of NaCl in 30 grams of salt by dividing the mass of the salt (30 g) by the molar mass of NaCl (58.5 g/mol):
[
\text{Moles of NaCl} = \frac{30 \, \text{g}}{58.5 \, \text{g/mol}} \approx 0.513 \, \text{moles}
]
Step 3: Conclusion
Thus, 30 grams of sodium chloride (NaCl) is approximately 0.513 moles of NaCl.
Explanation
This calculation is based on the relationship between mass, molar mass, and the number of moles. Moles are a way to count chemical entities, such as atoms or molecules, using a standard unit. The molar mass is the mass of one mole of a substance, typically given in grams per mole (g/mol). For NaCl, the molar mass is 58.5 g/mol, which means one mole of NaCl weighs 58.5 grams. By dividing the given mass of NaCl (30 grams) by its molar mass (58.5 g/mol), we determine how many moles are present in that mass. This concept is fundamental in chemistry for converting between grams and moles, enabling the calculation of quantities in chemical reactions.