The thyroid hormone thyroxine has the molecular formula C15 H11 NO4 I4 . Calculate the mass perc

The thyroid hormone thyroxine has the molecular formula C15...

Key Concepts

Mass Percent Calculation

Mass percent is determined by dividing the mass contribution of each element within a molecule by the total molar mass of the compound and then multiplying by 100. This calculation provides the percentage by mass of each element, offering insight into the composition and proportion of the elements present in the substance.

Molecular Formula

The molecular formula represents the number and types of atoms present in a molecule, providing a basic blueprint from which other properties, such as molar mass and elemental proportions, are derived. It is the starting point for many calculations in chemistry, including stoichiometric computations and determining mass percent composition.

Molar Mass Calculation

Calculating the molar mass involves adding the products of the atomic masses and the number of atoms for each element specified in the molecular formula. This total mass of one mole of the compound is essential for converting between mass and moles and forms the denominator in mass percent calculations.

Atomic Weights

Atomic weights are the average masses of atoms of an element, usually found on the periodic table. They are critical in quantifying the mass contribution of each element within a compound, enabling precise computation of the molar mass and subsequently the mass percent of each component.

Transcript

00:03 Okay, this is going to be a bit of a longer one because it's given us a pretty big formula.

00:09 We've got c -15 -h -11 n -o -4 -i -4.

00:20 Okay, and it wants to know what the percent composition is of each of those elements in this formula by mass.

00:28 Okay, so just like the other present composition questions we've done, the first thing we've got to do here is add up the total molar mass of this compound, and we're going to do it by breaking it down into the individual elements.

00:42 So we're going to say carbon, hydrogen, nitrogen, oxygen, and iodine.

00:50 If we look on the periodic table, we can see that carbon has a molar mass or atomic weight of 12.

00:58 You look right here.

01:00 Okay, hydrogen is one, oxygen is 16, nitrogen is 14, so they're all pretty common.

01:10 The one that you might have a harder time remembering is iodine, which is 127.

01:18 Okay, so let's write all these down.

01:19 So hydrogen was one, nitrogen was 14, oxygen was 16, iodine was 127.

01:28 Then we're going to multiply each of these by how many of that element we have.

01:33 So the carbon gets multiplied by 15, hydrogen by 11, nitrogen, there's just one of because there's no subscript there, oxygen times 4, and iodine times 4.

01:45 So a couple of these are going to be simpler than the others.

01:53 These other two we might have to bust out our calculator for.

01:58 12 times 15 is 180, and then 127 times 4 is 508.

02:08 So up here for the carbon, we would have 180...

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