Final answer:
The correct formula to enter in cell K6 for the Excel model is =B6*E6. This calculation multiplies the 'Quantity' by 'Average atomic mass (a m u)' to compute the 'Subtotal (a m u)'.
Step-by-step explanation:
The formula to be entered in cell K6 (and copied to K7:K12) in the Excel model is =B6*E6. This formula performs the operation to calculate the 'Subtotal (a m u)' by multiplying the 'Quantity' (found in column B) by the 'Average atomic mass (a m u)' (found in column E) for each element listed in the table.
For example, to find the formula mass of NaCl which is provided in the table, you would multiply the quantity of Na (1) by its average atomic mass (22.99 amu) to get 22.99 amu for sodium (Na) and repeat the process for chlorine (Cl), which has a quantity of 1 and an average atomic mass of 35.45 amu, resulting in a subtotal of 35.45 amu for chlorine. To find the formula mass of the compound, you sum the subtotals giving 58.44 amu for NaCl.