Atomic Mass

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

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

Tags

NGSS.MS-PS1-1

Calculate the average atomic mass of silver.

• 106.38649amu
• 111.91896amu
• 107.8677amu
• 121

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

Calcium has three different isotopes. One has a mass of 35.00 amu; another has a mass of 41.00 amu; and another has a mass of 40.00 amu. Which isotope is the most abundant of the three?

• 40.00 amu
• 41.00 amu
• 35.00 amu
• impossible to tell

Tags

NGSS.MS-PS1-1

Do the following atoms belong to the same element? Explain
       Aluminum-27
       An atom with 14 protons and 13 neutrons

• Yes because they have the same number of protons
• Yes because they have the same mass
• No because they have different number of protons
• No because they have different number of neutrons

Tags

NGSS.MS-PS1-1

An element has three isotopes. Given the abundances and relative masses, calculate the average atomic mass and determine (from the periodic table) which element it is.

Abundances | Relative masses

0.005% | 234.04 amu

0.720% | 235.04 amu

99.275% | 238.05 amu

• Uranium (#92, Atomic Mass: 238.03 amu)

• Fluorine (#9, Atomic Mass: 19.00 amu)

• Mercury (#89, Atomic Mass: 200.59 amu)

• Polonium (#84 209 amu)

Tags

NGSS.HS-PS1-8

Rubidium has two naturally occurring isotopes, ⁸⁵Rb (relative mass 84.9118 amu) and ⁸⁷Rb (relative mass 86.9092 amu). The abundance of ⁸⁷Rb is 27.8%, If rubidium has an average atomic mass of 85.47 amu, what is the % abundance of ⁸⁵Rb (in percent)?

• 27.9%

• 72.1%

• 74.63%

• 34.29%

Tags

NGSS.HS-PS1-7

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.MS-PS1-2

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