# Calculate the mass, in grams, of 2.54 times 10^{-2} mol of CdS.

## Question:

Calculate the mass, in grams, of {eq}\rm 2.54 \times 10^{-2}\ mol {/eq} of {eq}\rm CdS {/eq}.

## Finding Molar Mass of Compounds

The molar mass of an element can be directly obtained from a periodic table. It is typically given in units of g/mol. For compounds however, where two or more elements are chemically combined together, it is necessary to compute the molar mass by adding up the atomic masses of each of the elements, taking into consideration how many atoms are there in the molecule.

The molecule of interest is cadmium sulfide, CdS. The atomic mass of cadmium (Cd) is 112.4 and that of sulfur (S) is 32.1. Hence, the molar mass of this compound is:

{eq}112.4 + 32.1 = 144.5 \ g/mol {/eq}.

Now, we have {eq}2.54 \times 10^{-2} \ mol {/eq} of the compound. Its mass, in grams, would be:

{eq}2.54 \times 10^{-2} \ mol \times 144.5 \ g/mol = 3.67 \ g {/eq}.