Average Atomic Mass Calculations

What is the average atomic mass?

• The sum of the masses of its isotopes, each multiplied by its natural abundance

• The total number of protons in an element

• The total number of neutrons in an element

• The weight of an electron

The average atomic mass on the periodic table is found from...

• calculating the weighted average mass of all the isotopes of that element

• Calculating different types of elements together

• calculations the average of all elements in that period together.

• making a guess about how much all the isotopes might wiegh together.

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu

• 42.19 amu

• 10.43 amu

• 40.04 amu

An element has two naturally occurring isotopes. One is 10.013 amu and is 19.9% abundant. The other is 11.01 amu and is 80.1% abundant. What is the average atomic mass? What element is it?

• 9.012, Beryllium

• 12.011, Carbon

• 6.941, Lithium

• 10.812, Boron

What is the average atomic mass for thallium, Tl, if there are two isotopes with the following masses and abundances? Tl-203 has a mass of 203 amu with an abundance of 29.5 % Tl-205 has a mass of 205 amu with an abundance of 70.5 %

• 203.12 amu

• 204.31 amu

• 204.41 amu

• 204.0 amu

Tags

NGSS.HS-PS1-7

Calculate the average atomic mass of the element iron (Fe) using the following data:

[Isotope / % abundance]

[Iron 54 / 6% ] [Iron 56 / 92% ] [ Iron 57 / 2% ]

• 53.7 amu

• 54.9 amu

• 5592.0 amu

• 55.9 amu

An element has two naturally occurring isotopes. One is 10.013 amu and is 19.9% abundant. The other is 11.01 amu and is 80.1% abundant. What is the average atomic mass? What element is it?

• 15.99, Oxygen

• 10.81, Boron

• 10.81, Oxygen

• 15.99, Boron

A sample of cesium is 75% Cs-133, 20% Cs-132, and 5% Cs-134. What is the average atomic mass?

• 132.97 amu

• 133.00 amu

• 133.16 amu

• 132.85 amu

Tags

NGSS.MS-PS1-1

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
What is the average mass of this element?

• 74.92 amu

• 24.97 amu

• 75.01 amu

• 74.51 amu

Tags

NGSS.MS-PS1-2

What is the average atomic mass of an element with isotopes having masses of 10 amu (20% abundance) and 12 amu (80% abundance)?

• 10.4 amu

• 11.6 amu

• 12.0 amu

• 10.0 amu