Final Answer:
The mass of 2.79 × 10²² helium atoms, expressed in grams to three significant figures, is 4.66 × 10¹ g. Thus, the correct answer is A) 4.66 × 10¹ g.
Step-by-step explanation:
To calculate the mass of a given number of atoms, we need to know the atomic mass of the element in question. Helium has an atomic mass of approximately 4 u (where u is the unified atomic mass unit). This means that one mole of helium (6.02 × 10²³ helium atoms) has a mass of 4 grams.
To find the mass of 2.79 × 10²² helium atoms, we first convert this number to moles:
2.79 × 10²² helium atoms = (2.79 × 10²²) / (6.02 × 10²³) mol = 0.465 mol
Next, we find the mass of this amount of helium:
mass = (0.465 mol) × (4 g / mol) = 4.66 × 10¹ g (rounded to three significant figures)
Therefore, the mass of 2.79 × 10²² helium atoms is approximately 4.7 grams. This calculation demonstrates the relationship between the number of atoms and their corresponding mass, as well as the importance of using significant figures in scientific calculations.
Thus, the correct answer is A) 4.66 × 10¹ g.