 ## General Chemistry

Learn the toughest concepts covered in Chemistry with step-by-step video tutorials and practice problems by world-class tutors

2. Atoms & Elements

# Calculating Molar Mass

Molar Mass is a physical property that represents the mass of a substance divided by the amount of that substance.

Calculating Molar Mass
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concept

## Calculating Molar Mass 1m
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not Moeller. Mass is a physical property that represents the mass of a substance divided by the amount of that substance we're gonna say. The S I unit for Mass is kilograms and the S I unit for the amount of a substance is moles. But more mass is generally shown as being in units off grams per mole. Remember, when we see our shaded purple boxes, that means that's a definition or some type of formula you need to memorize. In this case, you need to memorize the molar mass formula. Moeller mass itself equals grams per mole. And what you also need to realize is that Mueller Mass is just one term that can talk about this relationship of grams per mole. Besides Moeller, Mass, you might also here refer to ass mult Mueller wait. Molecular weight or molecular mass. So just remember all of these air talking about the same thing. They're all referring to the relationship off grams per mole, the mass of a substance divided by the amount of that substance

The units for molar mass are in grams per mole.

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example

## Calculating Molar Mass Example 1 3m
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the example. Question says, calculate the molar mass of the compound NH 42 s 04 In order to do that, we're gonna follow each of the following steps. Alright, So step one, you have to count the number of each element within the given compound. Now, if the elements are within parentheses, just remember to distribute the subscript thio each not to each element. Alright, So within these parentheses we have NH four. That means we have one nitrogen, four hydrogen and this sub script of to what happens here is that too gets distributed. So it becomes two times one which will give us to nitrogen and then we have to times four, which will give us eight hydrogen. We're done with everything in parentheses. Next, Let's look at the S 04 So s 04 there's only one sulfur there. So there we know that there's a one that we don't see, So there's just one sulfur and then we see that there's four oxygen's, so we've successfully counted each of these elements within the compound. Next, find the atomic masses of each element from the periodic table. So we have nitrogen, hydrogen, sulfur and oxygen. Remember that the atomic mass is the number that is not. A whole number, usually has decimal places. That's because it's the average of all the isotopes for that particular element. So we have 14.1 g per mole, 1.8 g per mole, 32.7 g per mole and 16 roughly grams per mole for oxygen. The numbers on top are the atomic numbers, so let's not worry about those next, you're gonna multiply together the number of each element with their atomic masses from the periodic table. So from step one, we found out we had to nitrogen. Eight hydrogen, one sulfur and four oxygen's. Now multiplying them with their atomic masses gives us totals here. Now these new totals will be 28. There'll be 8. 32.7 and 64. Now that we have each of those totals, Step four is you add up the totals after multiplication to determine the molar mass off the compound. So we take all these numbers, we add them all up together. When we do that, we're going to get a total of 1 32. g per mole, so this would represent the Mueller Mass of our compound. So these are the steps you must always use always employ in order to determine the molar mass of any compound you come face to face with. So now that we know how to do that, let's continue onward with calculating Mueller, Mass.
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Problem

Calculate the molecular weight of C3H5N3O3.

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Problem

The reaction between nickel metal and hydrochloric acid is not a simple dissolution. The product formed is NiCl2 • 6 H2O (s), nickel (II) chloride hexahydrate, which has exactly 6 waters of hydration in the crystal lattice for every nickel ion. What is the molar mass of nickel (II) chloride hexahydrate, NiCl2 • 6 H2O (s)?

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Problem

What is the molar mass of diazepam also known as Valium if 0.05570 mol weighs 15.86 g? 