Calculating Average Atomic Mass

The video tutorial by Miss Near explains how to calculate the average atomic mass, which is the weighted average of the masses of different isotopes. The tutorial includes three examples: lithium, magnesium, and silicon isotopes. Each example demonstrates the process of converting percentages to decimals, multiplying atomic masses by their respective abundances, and applying significant figures to obtain the final average atomic mass. The video emphasizes the importance of predicting the outcome based on isotope abundances and checking the final answer for accuracy.

What is the average atomic mass?

• The sum of the masses of all isotopes

• The weighted average of the masses of different isotopes

• The average mass of the isotopes without considering their abundance

• The mass of the most abundant isotope

Which isotope of lithium has a higher abundance?

• Lithium-6

• Cannot be determined

• Both have equal abundance

• Lithium-7

How do you convert a percentage to a decimal?

• Move the decimal point two places to the right

• Multiply by 100

• Divide by 1000

• Move the decimal point two places to the left

What is the significance of significant figures in calculations?

• They make the numbers look neat

• They are used only in subtraction

• They ensure precision and accuracy

• They are used only in addition

Which magnesium isotope has the highest abundance?

• Magnesium-24

• Magnesium-25

• All have equal abundance

• Magnesium-26

What is the first step in calculating the average atomic mass of magnesium isotopes?

• Multiply the masses by their abundances

• Predict the average atomic mass

• Convert the percentages to decimals

• Add the masses of all isotopes

How many significant figures should the result have when multiplying 24.98584 by 0.1013?

• Five

• Seven

• Four

• Three

What is the predicted average atomic mass for silicon isotopes based on their abundances?

• Close to 27

• Close to 28

• Close to 29

• Close to 30

How do you write 92.23% as a decimal?

• 92.23

• 0.9223

• 9.223

• 0.09223

What is the final average atomic mass of silicon isotopes?

• 28.10 amu

• 28.1 amu

• 28.096 amu

• 28.00 amu