### Note the Pattern

The molar mass of any type of substance is its atomic mass, molecular mass, or formula mass in grams per mole.

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The routine table lists the atomic mass of carbon as 12.011 amu; the average molar mass of carbon—the mass of 6.022 × 1023 carbon atoms—is therefore 12.011 g/mol:

Substance (formula) Atomic, Molecular, or Formula Mass (amu) Molar Mass (g/mol)
carbon (C) 12.011 (atomic mass) 12.011
ethanol (C2H5OH) 46.069 (molecular mass) 46.069
calcium phosphate 310.177 (formula mass) 310.177

The molar mass of naturally developing carbon is different from that of carbon-12 and is not an integer bereason carbon occurs as a mixture of carbon-12, carbon-13, and carbon-14. One mole of carbon still has 6.022 × 1023 carbon atoms, however 98.89% of those atoms are carbon-12, 1.11% are carbon-13, and also a trace (around 1 atom in 1012) are carbon-14. (For more information, view Section 1.6 ) Similarly, the molar mass of uranium is 238.03 g/mol, and also the molar mass of iodine is 126.90 g/mol. When we resolve facets such as iodine and also sulhair, which take place as a diatomic molecule (I2) and also a polyatomic molecule (S8), respectively, molar mass typically refers to the mass of 1 mol of atoms of the element—in this instance I and also S, not to the mass of 1 mol of molecules of the facet (I2 and also S8).

The molar mass of ethanol is the mass of ethanol (C2H5OH) that contains 6.022 × 1023 ethanol molecules. As you calculated in Example 1, the molecular mass of ethanol is 46.069 amu. Due to the fact that 1 mol of ethanol consists of 2 mol of carbon atoms (2 × 12.011 g), 6 mol of hydrogen atoms (6 × 1.0079 g), and also 1 mol of oxygen atoms (1 × 15.9994 g), its molar mass is 46.069 g/mol. Similarly, the formula mass of calcium phosphate is 310.177 amu, so its molar mass is 310.177 g/mol. This is the mass of calcium phosphate that has 6.022 × 1023 formula systems.

The mole is the basis of quantitative nlinux.orgistry. It gives nlinux.orgists through a means to transform conveniently in between the mass of a substance and the variety of individual atoms, molecules, or formula units of that substance. Conversely, it allows nlinux.orgists to calculate the mass of a substance necessary to acquire a wanted number of atoms, molecules, or formula systems. For instance, to transform moles of a substance to mass, we use the relationship

( (moles)(molar ; mass) ightarrowhead mass ag1.71 )

or, more especially,

( molesleft ( dfracgramsmole appropriate ) = grams )​

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The mass of 1.75 mol of S2Cl2 is calculated as follows:

( moles; S_2Cl_2 left = mass; S_2Cl_2 )

( 1.75; mol; S_2Cl_2left ( dfrac135.036; g; S_2Cl_21;mol;S_2Cl_2 ideal )=236;g; S_2Cl_2 )

B The formula mass of Ca(ClO)2 is obtained as follows:

 1Ca (1 atom )(40.078 amu/atom) = 40.078 amu 2Cl (2 atoms)(35.453 amu/atom) = 70.906 amu 2O (2 atoms)(15.9994 amu/atom) = 31.9988 amu Ca(ClO)2 formula mass of Ca(ClO)2 = 142.983 amu

The molar mass of Ca(ClO)2 is 142.983 g/mol

( moles; Caleft ( ClO ight )_2left < dfracmolar; mass; Caleft ( ClO appropriate )_21; mol; Caleft ( ClO ideal )_2 ideal >=mass; Caleft ( ClO appropriate )_2 )

( 1.75; mol; Caleft ( ClO est )_2left < dfrac142.983; g Caleft ( ClO ideal )_21; mol; Caleft ( ClO est )_2 ideal >=250.; g; Caleft ( ClO ideal )_2 )​

Exercise

Calculate the mass of 0.0122 mol of each compound.

Si3N4 (silsymbol nitride), provided as bearings and also rollers (CH3)3N (trimethylamine), a corrosion inhibitor