Isotopic Abundance and Molar Mass Quiz

What is the primary tool used by chemists to determine isotopic abundance?

• Infrared spectrometer

• Nuclear magnetic resonance

• Gas chromatograph

• Mass spectrometer

How do you convert percentage abundance to a decimal for calculations?

• Divide by 100

• Multiply by 100

• Divide by 10

• Add 1 to the percentage

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

• Because isotopes have different chemical properties

• Because isotopes have different electron configurations

• Because isotopes have different abundances

• Because isotopes have different atomic numbers

In the analogy with test scores, what was the incorrect method of averaging?

• Using the mode of the scores

• Using the median score

• Averaging the highest and lowest scores

• Adding all scores and dividing by the number of scores

What is the average molar mass of copper if the isotopes are 63 and 65 with abundances of 69.1% and 30.9% respectively?

• 63.00

• 65.00

• 64.00

• 63.62

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

• Subtract the smallest atomic mass from the largest

• Multiply atomic masses by their abundances

• Convert percentage abundances to decimals

• Add the atomic masses

How do you express the probability of an isotope in a reverse calculation?

• As a fraction

• As a percentage

• As a decimal

• As a whole number

What is the equation used to find the abundance of isotopes from the average molar mass?

• Average molar mass = mass1 * mass2

• Average molar mass = (mass1 + mass2) / 2

• Average molar mass = (mass1 * abundance1) + (mass2 * abundance2)

• Average molar mass = mass1 + mass2

What is the calculated abundance of copper-65 if the average molar mass is 63.62?

• 0.31

• 0.69

• 0.50

• 0.25

Why is it not possible to determine isotopic abundance with more than two isotopes using the reverse calculation method?

• It becomes too complicated

• It is not allowed by scientific standards

• It is not possible to measure accurately

• It requires complex mathematical tools