Final answer:
Formula mass is a key concept in Chemistry, used to calculate the mass of a compound by summing the subtotals of atomic masses multiplied by the quantity of each element present within the compound.
Step-by-step explanation:
A formula mass is a set of instructions used to perform calculations on values in a worksheet. The table provided appears to be calculating the formula mass of a compound using the quantity of each element in the compound and their respective average atomic mass. Each element's quantity is multiplied by its atomic mass to yield the subtotal in atomic mass units (a m u), and then these subtotals are summed to arrive at the total formula mass of the compound. For instance, in the chemical equation, if a coefficient is present, it indicates the number of each molecule or formula unit in the balanced equation.
In the provided table, the quantity of "Na" and "Cl" is each "1," as shown in the "Quantity" column. The multiplication operation is applied to these quantities and the respective average atomic mass of each element. The resulting products are then listed in the "Subtotal (a m u)" column. The final cell in this column under the thick black line gives the formula mass, which is the sum of the subtotals of all individual elements within the chemical compound.