Note that this same approach may be used when the molar mass (g/mol) instead of the molecular mass (amu) is used. In this case, we are merely considering one mole of empirical formula units and molecules, as opposed to single units and molecules.
As given to you, the molecular mass, M r, is most likely the relative molecular mass, sometimes called molecular weight, which is defined as molecular mass divided by 1 12th of the mass of a single, unbound carbon-12 atom. relative molecular mass = molecular mass 1 u. For water, the relative molecular mass is. M r = 18.015u 1u = 18.015.
In each case, the number of grams in 1 mol is the same as the number of atomic mass units that describe the atomic mass, the molecular mass, or the formula mass, respectively. The periodic table lists the atomic mass of carbon as 12.011 amu; the average molar mass of carbon—the mass of 6.022 × 10 23 carbon atoms—is therefore 12.011 g/mol:
First calculate the molar mass of the unknown gas; Determine the identity of the gas by comparing the calculated molar mass to molar masses of known gases. Solution: A Since we are at STP, we can use the following equation to calculate molar mass: \[MM = \rho \cdot 22.4 L/mol\] \[MM = \rm 1.783 g/L \cdot 22.4 L/mol\] \[MM = \rm 39.9 g/mol\]
Solution. To calculate the percent composition, the masses of C, H, and O in a known mass of C 9 H 8 O 4 are needed. It is convenient to consider 1 mol of C 9 H 8 O 4 and use its molar mass (180.159 g/mole, determined from the chemical formula) to calculate the percentages of each of its elements: %C = 9mol C×molar mass C molar massC9H8O4 ×
MHg2Br2 = mHg2Br2 nHg2Br2 = 560.98 g mol−1 M Hg 2 Br 2 = m Hg 2 Br 2 n Hg 2 Br 2 = 560.98 g mol − 1. The molar mass is numerically the same as the atomic or molecular weight, but it has units of grams per mole. The equation, which defines the molar mass, has the same form as those defining density, and the Avogadro constant.
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is molecular mass and molar mass the same
