Find the average atomic mass for boron if 19.9% of boron atoms have a mass of 10.0129371 amu and 80.1% have a mass of 11.0093055 amu. Round to 3 significant figures.

Average atomic mass  = 10.8  amu

Explanation:

Given data:

Average atomic mass = ?

Percentage of boron having mass 10.0129371 amu = 19.9%

Percentage of boron having mass 11.0093055 amu = 80.1%

Solution:

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

Average atomic mass  = (19.9×10.0129371 )+(80.1×11.0093055) /100

Average atomic mass =  199.3 + 881.8 / 100

Average atomic mass = 1081.1  / 100

Average atomic mass  = 10.8  amu.

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.

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