Learning ObjectiveConvert in between the mass and also the variety of moles, and the variety of atoms, in a offered sample that compound
Key PointsThe molar fixed of a compound is equal to the amount of the atom masses the its constituent atoms in g/mol.Although over there is no physical way of measure the variety of moles that a compound, we deserve to relate that mass to the variety of moles by using the compound’s molar mass together a straight conversion factor.To convert in between mass and number of moles, you can use the molar massive of the substance. Then, you can use Avogadro’s number to transform the number of moles to variety of atoms.

You are watching: How many moles of helium are in 16 g of the element

TermsmoleThe amount of problem that has as plenty of elementary entities together there are atoms in 12 g the carbon-12.dimensional analysisThe analysis of the relationships between different physical amounts by identifying their an essential dimensions (such as length, mass, time, and also electric charge) and also units of measure up (such together miles vs. Kilometers, or pounds vs. Kilograms vs. Grams) and tracking this dimensions as calculations or comparisons are performed.molar massthe mass of a offered substance (chemical facet or chemical compound) divided by its lot of problem (mol), in g/mol.

Chemists typically use the mole together the unit for the variety of atoms or molecule of a material. One mole (abbreviated mol) is same to 6.022×1023 molecular reality (Avogadro’s number), and also each facet has a various molar mass depending on the weight of 6.022×1023 the its atoms (1 mole). The molar fixed of any element have the right to be identified by finding the atomic mass of the facet on the periodic table. For example, if the atom mass the sulfer (S) is 32.066 amu, climate its molar massive is 32.066 g/mol.

By recognizing the relationship between the molar massive (g/mol), mole (mol), and also particles, scientists can use dimensional evaluation convert in between mass, variety of moles and number of atoms very easily. Converting between mass, moles, and also particlesThis flowchart illustrates the relationships in between mass, moles, and particles. These relationships can be supplied to convert between units.

## Determining the Molar fixed of a Compound

In a link of NaOH, the molar fixed of Na alone is 23 g/mol, the molar massive of O is 16 g/mol, and also H is 1 g/mol. What is the molar mass of NaOH?

Na+O+H=NaOH

23 space extg/mol +16 space extg/mol+ 1 space extg/mol = 40 space extg/mol

The molar massive of the compound NaOH is 40 g/mol.

## Converting fixed to variety of Moles

How plenty of moles of NaOH are current in 90 g the NaOH?

Since the molar mass of NaOH is 40 g/mol, we deserve to divide the 90 g the NaOH by the molar mass (40 g/mol) to discover the mole of NaOH. This the exact same as multiply by the mutual of 40 g/mol.

If the equation is i ordered it correctly, the mass devices (g) publication out and leave moles together the unit.

90 g space extNaOH imes frac1 space mol40 g = 2.25 space extmol NaOH

There space 2.25 moles of NaOH in 90g that NaOH.

## Converting between Mass, number of Moles, and variety of Atoms

How countless moles and how numerous atoms are had in 10.0 g the nickel?

According come the regular table, the atom mass of nickel (Ni) is 58.69 amu, which method that the molar massive of nickel is 58.69 g/mol. Therefore, we can divide 10.0 g the Ni by the molar mass of Ni to uncover the number of moles present.

Using dimensional analysis, the is possible to recognize that:

10:g:Ni imes frac1:mol Ni58.69g Ni = 0.170: mol:Ni

To recognize the number of atoms, convert the moles of Ni to atoms utilizing Avogadro’s number:

0.170:moles:Ni imes frac 6.022×10^23 atom Ni1:mol Ni = 1.02 imes10^23:atoms:Ni

Given a sample’s fixed and number of moles in the sample, the is also feasible to calculate the sample’s molecule mass by separating the mass by the variety of moles to calculate g/mol.

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What is the molar massive of methane (CH4) if there room 0.623 mole in a 10.0g sample?

frac10.0 g CH_40.623 mol CH_4 = 16.05 g/mol CH_4

The molar massive of CH4 is 16.05 g/mol.

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