28.0 grams of sodium are how many moles?
The Correct Answer and Explanation is:
To find out how many moles are in 28.0 grams of sodium (Na), we use the formula:
[
\text{Moles} = \frac{\text{mass (grams)}}{\text{molar mass (g/mol)}}
]
Step 1: Determine the Molar Mass of Sodium
Sodium has an atomic number of 11 on the periodic table, and its atomic weight is approximately 22.99 g/mol. This value is the molar mass of sodium and represents the mass of one mole of sodium atoms.
Step 2: Plug in the Values
Now, we can substitute the values into the formula:
[
\text{Moles of Na} = \frac{28.0 \text{ grams}}{22.99 \text{ g/mol}}
]
Step 3: Perform the Calculation
Calculating this gives:
[
\text{Moles of Na} = \frac{28.0}{22.99} \approx 1.22 \text{ moles}
]
Conclusion
Thus, 28.0 grams of sodium is approximately 1.22 moles.
Explanation of Moles and Molar Mass
The concept of a mole is a fundamental aspect of chemistry, serving as a bridge between the atomic scale and the macroscopic scale we observe in the laboratory. One mole of any substance contains exactly (6.022 \times 10^{23}) entities (atoms, molecules, etc.), known as Avogadro’s number. This constant allows chemists to count quantities of atoms and molecules using grams, which are easier to measure.
Molar mass, which is the mass of one mole of a substance, varies between elements. For sodium, the molar mass is derived from its atomic weight, which reflects the average mass of its isotopes. When performing stoichiometric calculations, understanding how to convert grams to moles is essential for determining the amount of reactants and products involved in chemical reactions. This conversion is crucial in laboratory settings, particularly when preparing solutions, conducting reactions, or analyzing products. Thus, knowing how to calculate moles from grams enables accurate quantitative analysis in various chemical processes.