## Molecular weight of Aluminium

Molar mass of Al = **26.981538 g/mol**

Convert grams Aluminium to moles or moles Aluminium to grams

Element | Symbol | Atomic Mass | # of Atoms | Mass Percent |

Aluminium | Al | 26.981538 | 1 | 100.000% |

In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.

Finding molar mass starts with units of grams per mole (g/mol). When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula.

A common request on this site is to convert grams to moles. To complete this calculation, you have to know what substance you are trying to convert. The reason is that the molar mass of the substance affects the conversion. This site explains how to find molar mass.

Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.

Formula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. These relative weights computed from the chemical equation are sometimes called equation weights.

If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100.

The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. We use the most common isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.

## 6.2: Atomic and Molar Masses

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Skills to Develop

- To learn how the masses of moles of atoms and molecules are expressed.

Now that we have introduced the mole and practiced using it as a conversion factor, we ask the obvious question: why is the mole *that particular* number of things? Why is it \(6.022 \times 10^{23}\) and not \(1 \times 10^{23}\) or even \(1 \times 10^{20}\)?

The number in a mole, Avogadro’s number, is related to the relative sizes of the atomic mass unit and gram mass units. Whereas one hydrogen atom has a mass of approximately 1 u, 1 mol of H atoms has a mass of approximately 1 *gram*. And whereas one sodium atom has an approximate mass of 23 u, 1 mol of Na atoms has an approximate mass of 23 *grams*.

*One mole of a substance has the same mass in grams that one atom or molecule has in atomic mass units.* The numbers in the periodic table that we identified as the atomic masses of the atoms not only tell us the mass of one atom in u but also tell us the mass of 1 mol of atoms in grams.

One mole of a substance has the same mass in grams that one atom or molecule has in atomic mass units.

Example \(\PageIndex{1}\): Moles to Mass Conversion with Elements

What is the mass of each quantity?

- 1 mol of Al atoms
- 2 mol of U atoms

**SOLUTION**

- One mole of Al atoms has a mass in grams that is numerically equivalent to the atomic mass of aluminum. The periodic table shows that the atomic mass (rounded to two decimal points) of Al is 26.98, so 1 mol of Al atoms has a mass of 26.98 g.
- According to the periodic table, 1 mol of U has a mass of 238.03 g, so the mass of 2 mol is twice that, or 476.06 g.

The mole concept can be extended to masses of formula units and molecules as well. The mass of 1 mol of molecules (or formula units) in grams is numerically equivalent to the mass of one molecule (or formula unit) in atomic mass units. For example, a single molecule of O_{2} has a mass of 32.00 u, and 1 mol of O_{2} molecules has a mass of 32.00 g. As with atomic mass unit–based masses, to obtain the mass of 1 mol of a substance, we simply sum the masses of the individual atoms in the formula of that substance. The mass of 1 mol of a substance is referred to as its molar mass, whether the substance is an element, an ionic compound, or a covalent compound.

Example \(\PageIndex{2}\): Moles to Mass Conversion with Compounds

What is the mass of 1 mol of each substance?

- NaCl
- bilirubin (C
_{33}H_{36}N_{4}O_{6}), the principal pigment present in bile (a liver secretion)

**SOLUTION**

Summing the molar masses of the atoms in the NaCl formula unit gives

1 Na molar mass: | 23.00 g |

1 Cl molar mass: | 35.45 g |

Total: | 58.45 g |

The mass of 1 mol of NaCl is 58.45 g.

- Multiplying the molar mass of each atom by the number of atoms of that type in bilirubin’s formula and adding the results, we get

33 C molar mass: | 33 × 12.01 g | 396.33 g |

36 H molar mass: | 36 × 1.01 = | 36.36 g |

4 N molar mass: | 4 × 14.00 = | 56.00 g |

6 O molar mass: | 6 × 16.00 = | 96.00 g |

Total: | 584.69 g |

The mass of 1 mol of bilirubin is 584.69 g.

Be careful when counting atoms. In formulas with polyatomic ions in parentheses, the subscript outside the parentheses is applied to every atom inside the parentheses. For example, the molar mass of Ba(OH)_{2} requires the sum of 1 mass of Ba, 2 masses of O, and 2 masses of H:

1 Ba molar mass: | 1 × 137.33 g = | 137.33 g |

2 O molar mass: | 2 × 16.00 g = | 32.00 g |

2 H molar mass: | 2 × 1.01 g = | 2.02 g |

Total: | 171.35 g |

Because molar mass is defined as the mass for 1 mol of a substance, we can refer to molar mass as grams per mole (g/mol). The division sign (/) implies “per,” and “1” is implied in the denominator. Thus, the molar mass of bilirubin can be expressed as 584.05 g/mol, which is read as “five hundred eighty four point zero five grams per mole.”

### Concept Review Exercises

- How are molar masses of the elements determined?
- How are molar masses of compounds determined?

### Answers

- Molar masses of the elements are the same numeric value as the masses of a single atom in atomic mass units but with different units, grams (per one mole).
- Molar masses of compounds are calculated by adding the molar masses of their atoms.

### Key Takeaway

- The mass of moles of atoms and molecules is expressed in units of grams.

### Exercises

What is the molar mass of Si? What is the molar mass of U?

What is the molar mass of FeCl

_{2}? What is the molar mass of FeCl_{3}?What is the molar mass of (NH

_{4})_{2}S? What is the molar mass of Ca(OH)_{2}?Aspirin (C

_{9}H_{8}O_{4}) is an analgesic (painkiller) and antipyretic (fever reducer). What is the molar mass of aspirin?

### Answers

- 28.09 g/mol; 238.00 g/mol
- 126.75 g/mol; 162.20 g/mol
- 68.15 g/mol; 74.10 g/mol
- 180.17 g/mol

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## Aluminum molar mass

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Molar Mass / Molecular Weight of Al2O3 (Aluminum oxide)Girl's cave. Touching the girl, in such an intimate place, he noticed that it was hot there, but not very humid, and he remembered that the guys said that. The girl should flow, then the member is inserted very well. He remembered one way to moisturize, soaked his palm in his saliva and lubricated the head of his penis.

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