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1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

6. Chemical Reactions & Quantities

Calculating Molar Mass

6. Chemical Reactions & Quantities

Calculating Molar Mass: Videos & Practice Problems

Video Lessons Practice Worksheet

Topic summary

Molar mass is a physical property defined as the mass of a substance divided by the amount of that substance, typically expressed in grams per mole (g/mol). It is essential to understand that molar mass, also known as molar weight, molecular weight, or molecular mass, represents the relationship between mass and the amount of substance. This concept is crucial in various chemical calculations, including stoichiometry and determining the yield of reactions. Remembering the formula for molar mass is vital for success in chemistry.

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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Calculating Molar Mass

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Calculating Molar Mass Video Summary

Molar mass is a crucial physical property that quantifies the mass of a substance relative to the amount of that substance. In scientific terms, the SI unit for mass is kilograms, while the SI unit for the amount of a substance is moles. However, molar mass is typically expressed in grams per mole (g/mol). It is essential to memorize the formula for molar mass, which can be represented as:

Molar Mass = \frac{\text{grams}}{\text{mole}}

It's important to note that the term "molar mass" is often used interchangeably with "molar weight," "molecular weight," or "molecular mass." Regardless of the terminology, all these terms refer to the same concept: the relationship of grams per mole, which indicates how much mass is present in a given amount of substance. Understanding this relationship is fundamental in various fields of chemistry, as it allows for the conversion between mass and moles, facilitating calculations in stoichiometry and other chemical analyses.

The units for molar mass are in grams per mole.

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Calculating Molar Mass Example 1

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Calculating Molar Mass Example 1 Video Summary

To calculate the molar mass of the compound $ \text{NH}_4\text{(SO}_4\text{)}_2 $, follow these systematic steps:

First, identify and count the number of each element in the compound. For the ammonium ion $ \text{NH}_4 $, there is 1 nitrogen (N) and 4 hydrogens (H). The subscript 2 outside the parentheses indicates that both the nitrogen and hydrogen counts must be multiplied by 2, resulting in 2 nitrogens and 8 hydrogens. Next, for the sulfate ion $ \text{SO}_4 $, there is 1 sulfur (S) and 4 oxygens (O). Thus, the total counts are:

Nitrogen: 2
Hydrogen: 8
Sulfur: 1
Oxygen: 4

Next, refer to the periodic table to find the atomic masses of each element:

Nitrogen (N): 14.01 g/mol
Hydrogen (H): 1.008 g/mol
Sulfur (S): 32.07 g/mol
Oxygen (O): 16.00 g/mol

Now, multiply the number of each element by its atomic mass:

For Nitrogen: $ 2 \times 14.01 = 28.02 \, \text{g/mol} $
For Hydrogen: $ 8 \times 1.008 = 8.064 \, \text{g/mol} $
For Sulfur: $ 1 \times 32.07 = 32.07 \, \text{g/mol} $
For Oxygen: $ 4 \times 16.00 = 64.00 \, \text{g/mol} $

Finally, add these totals together to find the molar mass of the compound:

\[\text{Total Molar Mass} = 28.02 + 8.064 + 32.07 + 64.00 = 132.154 \, \text{g/mol}\]

Thus, the molar mass of $ \text{NH}_4\text{(SO}_4\text{)}_2 $ is approximately 132.15 g/mol. This method can be applied to determine the molar mass of any compound you encounter.

Problem

Calculate the molecular weight of C₃H₅N₃O₃.

123.80 g/mol

131.10 g/mol

136.90 g/mol

147.10 g/mol

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)?

228.99 g/mol

231.01 g/mol

234.71 g/mol

237.69 g/mol

Problem

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

220.1 g/mol

241.4 g/mol

263.9 g/mol

284.7 g/mol

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What is the formula for calculating molar mass?

The formula for calculating molar mass is the mass of a substance divided by the amount of that substance. It is typically expressed in grams per mole (g/mol). Mathematically, it can be represented as:

$M = \frac{m}{n}$

where $M$ is the molar mass, $m$ is the mass of the substance in grams, and $n$ is the amount of substance in moles. This formula is essential for various chemical calculations, including stoichiometry and determining reaction yields.

How do you calculate the molar mass of a compound?

To calculate the molar mass of a compound, follow these steps:

Identify the chemical formula of the compound.
Determine the atomic masses of each element in the compound from the periodic table.
Multiply the atomic mass of each element by the number of atoms of that element in the compound.
Add the total masses of all the elements together to get the molar mass of the compound.

For example, to calculate the molar mass of water (H₂O):

Hydrogen (H) has an atomic mass of approximately 1 g/mol, and there are 2 hydrogen atoms.
Oxygen (O) has an atomic mass of approximately 16 g/mol, and there is 1 oxygen atom.

So, the molar mass of H₂O is:

$2 \times 1 + 16 = 18$ g/mol.

Why is molar mass important in chemistry?

Molar mass is crucial in chemistry because it allows chemists to convert between the mass of a substance and the amount of substance in moles. This conversion is essential for stoichiometric calculations, which involve determining the proportions of reactants and products in chemical reactions. Knowing the molar mass helps in calculating the yield of reactions, preparing solutions with precise concentrations, and understanding the properties of substances. Additionally, molar mass is fundamental in determining molecular formulas and understanding the composition of compounds. Overall, it is a key concept that underpins many aspects of chemical analysis and synthesis.

What is the difference between molar mass and molecular weight?

Molar mass and molecular weight are terms that are often used interchangeably, but they have subtle differences. Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is a physical property that relates the mass of a substance to the amount of substance. Molecular weight, on the other hand, is a dimensionless quantity that represents the sum of the atomic weights of all atoms in a molecule. While molar mass is used in practical calculations involving grams and moles, molecular weight is often used in theoretical contexts. Despite these differences, both terms ultimately describe the same concept: the mass of a given amount of substance.

How do you find the molar mass of an element?

To find the molar mass of an element, you need to look up its atomic mass on the periodic table. The atomic mass is usually listed below the element symbol and is expressed in atomic mass units (amu). For practical purposes in chemistry, the atomic mass in amu is numerically equivalent to the molar mass in grams per mole (g/mol). For example, the atomic mass of carbon (C) is approximately 12.01 amu, so the molar mass of carbon is 12.01 g/mol. This value represents the mass of one mole of carbon atoms.