How many grams are in 4.5 moles of sodium fluoride, NaF?
The correct answer and explanation is :
To find the number of grams in 4.5 moles of sodium fluoride (NaF), we need to use the concept of molar mass, which is the mass of one mole of a substance. The molar mass is typically expressed in grams per mole (g/mol).
Step-by-Step Calculation:
- Determine the molar mass of sodium fluoride (NaF):
Sodium fluoride (NaF) consists of two elements:
- Sodium (Na): The atomic mass of sodium is approximately 22.99 g/mol.
- Fluorine (F): The atomic mass of fluorine is approximately 19.00 g/mol. Therefore, the molar mass of NaF is the sum of the atomic masses of sodium and fluorine:
[
\text{Molar mass of NaF} = \text{Atomic mass of Na} + \text{Atomic mass of F}
]
[
\text{Molar mass of NaF} = 22.99 \, \text{g/mol} + 19.00 \, \text{g/mol} = 41.99 \, \text{g/mol}
]
- Use the formula to calculate the mass:
To calculate the mass in grams of a given number of moles, use the formula:
[
\text{Mass (g)} = \text{Moles} \times \text{Molar mass (g/mol)}
] Now, substitute the values:
[
\text{Mass (g)} = 4.5 \, \text{moles} \times 41.99 \, \text{g/mol}
]
[
\text{Mass (g)} = 189.955 \, \text{g}
] Rounded to the appropriate number of significant figures (based on the 4.5 moles given, which has two significant figures), the mass is:
[
\text{Mass (g)} = 190 \, \text{g}
]
Conclusion:
The mass of 4.5 moles of sodium fluoride (NaF) is 190 grams.
Explanation:
The concept of molar mass is crucial when converting between moles and grams. A mole is a standard quantity used to measure the amount of substance, just like a dozen represents 12 items. The molar mass allows you to translate moles into grams. By multiplying the number of moles by the molar mass of NaF, we can find the mass of sodium fluoride in grams.