Relative Atomic Mass and Isotopes

The video tutorial explains isotopic mass and its relation to carbon-12, highlighting the difference between isotopic mass and mass number. It defines relative atomic mass as the average mass of naturally occurring isotopes relative to carbon-12. The tutorial emphasizes the importance of isotopic abundance in calculating relative atomic mass, using chlorine as an example. A step-by-step calculation is provided, demonstrating how to account for the weighted average of isotopes. The tutorial concludes with a summary of key points.

What is isotopic mass primarily related to?

• The mass of an element compared to nitrogen

• The mass of an element compared to hydrogen

• The mass of an element compared to carbon-12

• The mass of an element compared to oxygen

Which of the following is NOT an isotopic form of chlorine?

• Chlorine-35

• Chlorine-36

• Chlorine-37

• Chlorine-38

What does the relative atomic mass (AR) represent?

• The sum of all isotopic masses

• The average mass of isotopes relative to carbon-12

• The mass of the most abundant isotope

• The mass of the heaviest isotope

How is the relative atomic mass different from the mass number?

• It is only applicable to synthetic elements

• It is always larger than the mass number

• It is a weighted average considering isotopic abundance

• It is a simple average of isotopic masses

Why can't we use a simple average to calculate the relative atomic mass?

• Because isotopes have different chemical properties

• Because isotopes have different abundances

• Because isotopes have the same mass

• Because isotopes are unstable

What is the relative abundance of chlorine-35 in naturally occurring chlorine?

• 75%

• 25%

• 100%

• 50%

How do you calculate the total mass of a sample of isotopes?

• By adding the masses of all isotopes

• By multiplying the mass of each isotope by its abundance and summing the results

• By dividing the mass of each isotope by its abundance

• By averaging the masses of all isotopes

What is the relative atomic mass of chlorine if 75% is chlorine-35 and 25% is chlorine-37?

• 34.5

• 35.5

• 36.0

• 37.0

Why is the relative atomic mass closer to 35 for chlorine?

• Because chlorine-35 is more abundant

• Because chlorine-37 is more abundant

• Because chlorine-35 is heavier

• Because both isotopes are equally abundant

What must be considered when calculating the relative atomic mass of an element?

• The temperature at which the element is found

• The color of the element

• The proportion of each isotope in the sample

• The chemical properties of isotopes