F.3 part b

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Kristina Rizo 2K
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F.3 part b

Postby Kristina Rizo 2K » Thu Oct 03, 2019 9:30 pm

The question states, "Without doing a calculation, estimate which element in nitric acid occurs with the greatest mass percentage." I am confused as to how I am supposed to eyeball the formula to guesstimate which would have the highest mass percentage. Am I looking at the mol ratio or the stoichiometric coefficients?

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Re: F.3 part b

Postby salvadorramos3k » Thu Oct 03, 2019 9:36 pm

If you refer back to the book in Example F.1, you can guess which will have the highest mass percentage based off of which of the elements is the heaviest. The formula is HNO3. Hydrogen contributes 1 gram, Nitrogen 14 grams, and Oxygen contributes 48 grams. So based off of this, we can guess that Oxygen will have the highest mass percentage :)

Lara Kristine Bacasen 1L
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Re: F.3 part b

Postby Lara Kristine Bacasen 1L » Thu Oct 03, 2019 9:38 pm

Okay so for this one you know the what the molecule of nitric acid is composed of HNO3. When you look at it think about how many atoms there are of each element and try to think of their individual masses as well. H is the lightest so it shouldn't have the largest mass composition. Now look at N and O and decide which one would take up the greatest percentage of the mass composition. Then you have your answer.

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Re: F.3 part b

Postby nicolely2F » Thu Oct 03, 2019 9:39 pm

The formula for nitric acid is HNO3. To answer this questions without doing any calculations, we can use our knowledge of atomic masses. We don't need exact numbers for this either, as long as you have a notion on the most common elements, some of which are H, N, and O. If you have some familiarity with chemical elements, you might be able to tell that:
1. The element with the greatest mass percentage is definitely not H, as it is both the lightest element in the periodic table and only present as one atom per mole of HNO3
2. O is slightly heavier than N, and that, along with the fact that there are 3 times more O atoms than there are N atoms per mole of HNO3, can tell you that the element we're looking for is O.

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