4. Calculate the average atomic mass of lithium, which occurs as two isotopes that have the following atomic masses and abundances in nature: 6.017 u, 7.30%
and 7.018 u, 92.70%.

The average atomic mass is 6.94 amu.

The Atomic mass of the first isotope = 6.017 amu

Atomic mas off second isotope = 7.018 amu

The abundance of first isotope = 7.30%

The abundance of second isotope = 92.70%

Average atomic mass  = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

= (7.30×6.017)+(92.70×7.018) /100

=  43.924 + 650.57 / 100

= 694.494 / 100

= 6.94 amu.

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Average atomic mass = 6.94 amu.

Explanation:

Given data:

Average atomic mass = ?

Atomic mass of first isotope = 6.017 amu

Atomic mas off second isotope = 7.018 amu

Abundance of fist isotope = 7.30%

Abundance of second isotope = 92.70%

Solution:

Average atomic mass  = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass  = (7.30×6.017)+(92.70×7.018) /100

Average atomic mass =  43.924 + 650.57 / 100

Average atomic mass  = 694.494 / 100

Average atomic mass = 6.94 amu.

answer: c.

explanation:

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.