Question

INTRODUCTION In week one, we studied the imortance of measurements in chemistry and conversions between systems, such as the imperial system and the metric system. There are other conversions used between moles (mol). toms, and grams (g). In the laboratory balances are used to measure the amount of a substance. However, case chemical reactions take place when particles interact, chemists need to be able to relate the mass of a substance to the number of articles present Therefore, the ability to convert between grams, moles, and atoms, is very important. The chemical formula of a con al formula of a compound is used to calculate the formula mass, the sum of the atomic masses O atonis in a molecule. The formula mass has units of amu, or atomic mass units. The formula mass is by multiplying the number of atoms in a molecule by the atomic mass of the atom found on the periodic table. For example, the formula mass of water. H.O is calculated as follows: urmula mass of H2O = |(2 H atoms). (1.01 am ) + (1 O atom) . (16,00 am 10.02 Water (H2O) has two H atoms, so the atomic mass of one atom (found on the periodic table) must be multiplied by two. As only one oxygen atom is in the compound, the atomic mass of an O atom is multiplied by the number one. Let's look at a slightly more difficult example, Take a minute and calculate the formula mass of the compound, aluminum carbonate, Al:(CO) in the box below. Show all of your work Show work here: Page 1

Answer 1

Formula mass of Al2(CO3)3

= (2 Al atoms $\times$ 26.98 amu ) + [ ( 1 C atom $\times$ 12.01 amu) + 3 O atoms $\times$ 16.00 amu ) $\times$ 3 ]

= 53.96 amu + (3 $\times$ 60.01) amu

= 53.96 amu + 180.03 amu

= 233.99 amu