How many atoms are present in 39.9 g of palladium (Pd) atoms?

Question

BlackTom AI · Accepted Answer

To determine how many atoms are in a given mass of palladium, start by identifying the molar mass of Pd, which is about 106.42 g per mole. Next, convert the mass to moles: 39.9 g ÷ 106.42 g/mol ≈ 0.3755 mol. The number of atoms is found by multiplying moles by Avogadro's number (6.022 × 10^23 atoms/mol): 0.3755 mol × 6.022 × 10^23 atoms/mol ≈ 2.26 × 10^23 atoms.

Now evaluate the answer choices:

A) 1.61 × 10^24: This is roughly 7 times larger than the computed value, which would correspond to about 2.66 moles, not 0.3755 mol. The discrepancy suggests an incorrect conversion or a misused molar mass.

B) 2.12 × 10^21: This is two orders of magnitude smaller than the correct result, indicating a misplacement of the exponent by about 100 times. Likely an error in converting moles to atoms.

C) 6.02 × 10^23: This number represents exactly one mole of atoms. Since the sample contains far less than a mole (≈0.376 mol), this would be correct only if the mass corresponded to one mole, which it does not.

D) 2.26 × 10^23: This matches the calculation outcome when multiplying 0.3755 mol by Avogadro's number, giving the correct order of magnitude and value for the number of Pd atoms in 39.9 g.

In summary, the correct approach uses the palladium molar mass to get moles, then multiplies by Avogadro's number to obtain atoms. The incorrect choices either overestimate by about a factor of a few or underestimate by two orders of magnitude, reflecting common pitfalls in unit conversion or exponent handling.

How many atoms are present in 39.9 g of palladium (Pd) atoms?单项选择题

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