Calculating Weighted Average Atomic Mass

What are the two main objectives of the lesson?

• To describe atomic mass unit and determine the weighted average atomic mass

• To describe atomic mass unit and calculate molecular mass

• To determine molecular mass and calculate isotopic abundance

• To describe isotopic abundance and calculate molecular mass

Why can't you simply average the masses of isotopes to find the average atomic mass?

• Because isotopes have different chemical properties

• Because the abundance of each isotope must be considered

• Because isotopes have different charges

• Because isotopes have different physical states

In the classroom analogy, why is it incorrect to average the ages of the students and the teacher directly?

• Because the ages are not whole numbers

• Because the ages are not in the same range

• Because the teacher's age is not relevant

• Because there are more students than the teacher

How do you calculate the average age of a classroom with different numbers of students in each age group?

• By multiplying the age of each group by the number of students in that group, summing these products, and dividing by the total number of students

• By averaging the ages of the students and the teacher

• By adding the ages and dividing by the number of age groups

• By taking the median age of the students

What is the simplified equation for calculating the average atomic mass?

• Sum of the product of the percentage and mass of each isotope divided by the number of isotopes

• Sum of the product of the percentage and mass of each isotope divided by 100

• Sum of the masses of all isotopes

• Sum of the percentages of all isotopes

Why can't individual atoms be counted to determine their average mass?

• Because atoms are too small to be counted individually

• Because atoms are always in motion

• Because atoms are not visible

• Because atoms have different charges

Given that 99.6% of nitrogen is nitrogen-14 and 0.4% is nitrogen-15, what is the average atomic mass of nitrogen?

• 14.07 amu

• 14.00 amu

• 15.00 amu

• 15.07 amu

What pattern is observed in the average atomic mass of an element?

• It is always the lowest isotopic mass

• It is always the highest isotopic mass

• It is closest to the mass of the most abundant isotope

• It is always exactly in the middle of the isotopic masses

Calculate the weighted average atomic mass for carbon given 98.90% is carbon-12 and 1.10% is carbon-13.

• 12.01 amu

• 13.01 amu

• 12.00 amu

• 13.00 amu

What is the unit used for atomic mass?

• Moles

• Atomic Mass Unit (amu)

• Kilograms

• Grams