Average Atomic Mass Re-Quiz

If an element has two isotopes with masses 10 amu and 12 amu, and their abundances are 25% and 75% respectively, what is the average atomic mass of the element?

• 13 amu

• 10.5 amu

• 11.5 amu

• 9 amu

If an element has three isotopes with masses 20 amu, 22 amu, and 24 amu, and their abundances are 10%, 20%, and 70% respectively, what is the average atomic mass of the element?

• 24.6 amu

• 22.4 amu

• 25.8 amu

• 23.2 amu

If an element has three isotopes with masses 30 amu, 32 amu, and 34 amu, and their abundances are 25%, 50%, and 25% respectively, what is the average atomic mass of the element?

• 33

• 35

• 32

• 31

If an element has two isotopes with masses 8 amu and 10 amu, and their abundances are 60% and 40% respectively, what is the average atomic mass of the element?

• 8.8 amu

• 10.4 amu

• 9.6 amu

• 9.2 amu

How many neutrons does the isotope below have?     ⁸⁹ ₃₆Kr

• 53
• 36
• 89
• 125

How many electrons does a ¹²⁷Te^2- ion have?

(ONLY write a number in the blank!)

Tags

NGSS.HS-PS1-1

How many electrons does a ¹³⁸Ba²⁺ ion have?

(ONLY write a number in the blank!)

How many electrons does a ⁴⁵Sc³⁺ ion have?

(ONLY write a number in the blank!)

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 76.20 amu.

The average mass of this element is ________ amu.

(Only write your answer rounded correctly to the 10ths decimal place!)

Answer explanation

75.2

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.

The average atomic mass of atom X is _____________amu.

(Only write your answer rounded correctly to the 100ths decimal place!)

Answer explanation

41.996 --> 42.00