Question

If potassium has three isotopes with masses 38.96, 39.93, and 40.96 and percent abundances of 93.26%, .01%, and 6.73%, how would you calculate average atomic mass?

Answer 1

To calculate the average atomic mass of potassium with its three isotopes, multiply the mass of each isotope by its decimal abundance, and add the values together to get the average atomic mass.

Step-by-step explanation:

To calculate the average atomic mass of an element with multiple isotopes, such as potassium which has three isotopes, you need to take into account the mass of each isotope and its relative natural abundance. The formula for calculating the average atomic mass is the sum of each isotope's mass multiplied by its decimal abundance. Here's the calculation for potassium:

• Isotope 1: mass = 38.96 amu, abundance = 93.26% or 0.9326 in decimal
• Isotope 2: mass = 39.93 amu, abundance = 0.01% or 0.0001 in decimal
• Isotope 3: mass = 40.96 amu, abundance = 6.73% or 0.0673 in decimal

Using these values, the average atomic mass of potassium would be:

(0.9326 × 38.96 amu) + (0.0001 × 39.93 amu) + (0.0673 × 40.96 amu) = average atomic mass

Simply perform the multiplications for each isotope and sum up the results to find the average atomic mass of potassium.