What is the mass of 91.4 moles of NH3 molecules?

Question

BlackTom AI · Accepted Answer

We are given a question about the mass corresponding to a certain amount of NH3 molecules expressed in moles and asked to select the correct numerical mass value from the options.

Option A: 2.58 × 10–21 g. This is extraordinarily small for 91.4 moles. To put it in perspective, even a single molecule has a mass on the order of 10^−23 g, so 91.4 moles (which contains on the order of 6.02×10^23 × 91.4 molecules) would not yield such a tiny mass. This option is inconsistent with the mole-to-gram conversion using molar mass, so it is incorrect.

Option B: 9.37 × 10^26 g. This is an astronomically large mass far exceeding any practical chemical quantity for a few tens of moles. The mass of a few dozen moles cannot approach 10^27 g (which is about the mass of something on a planetary scale), so this option is also incorrect.

Option C: 5.37 g. This is far smaller than the expected mass for 91.4 moles of NH3. Since the molar mass of NH3 is about 17 g per mole, 91.4 moles should weigh roughly 91.4 × 17 ≈ 1550 g. Therefore, this option underestimates the mass by about three orders of magnitude and is incorrect.

Option D: 1.56 × 10^3 g. This is the mass you would obtain by converting moles to grams using the molar mass. Using NH3 molar mass ≈ 17.034 g/mol, the mass is 91.4 mol × 17.034 g/mol ≈ 1557 g, which is about 1.56 × 10^3 g. This aligns with the standard mole-to-mass calculation for NH3 and is therefore consistent with the data given.

Option E: 17.03 g. This number matches the molar mass of NH3, not the total mass of 91.4 moles. It would be the mass of a single mole of NH3, not of 91.4 moles, so this option is incorrect for the question as stated.

In summary, options A, B, C, and E fail to reflect the correct application of molar mass to moles for the total mass of 91.4 moles, while option D provides the correct total mass when the molar mass is multiplied by the amount in moles. The calculation steps rely on using NH3 molar mass ≈ 17.034 g/mol and total mass = (moles) × (molar mass).

What is the mass of 91.4 moles of NH3 molecules?

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