The average atomic masses of some elements may vary, depending upon souces of their ores. naturally occurring boron consist of two isotopes with accurately known masses (10 b, 10.0129 amu and 11b, 11.0931 amu). the actual atomic mass of boron can vary grom 10.807 to 10819, depending on whether the mineral source is from turkey or the united states. calculate the percent abundances leading to the two values of the average atomic masses of boron from these two countries.

1) atomic mass 10.807

Percentage of 10B= 26.48%

Percentage of 11B= 73.52%

2) atomic mass 10.819

Percentage of 10B= 25.37%

Percentage of 11B= 74.63%

Explanation:

The average atomic mass of an element is the weighted average of the atomic masses of the isotopes of the element.

If a sources is rich in one kind of isotope then the atomic mass will be nearer to its value and if it is rich in another kind then the atomic mass will be nearer to its value.

Let us calculate the percentage abundance in each case.

a) Average atomic mass =

Average atomic mass = 10.807

Let the % of 10B isotope = x

% of 11B isotope =100-x

putting in the formula

Percentage of 11B= 100-26.48= 73.52%

a) Average atomic mass =

Average atomic mass = 10.819

Let the % of 10B isotope = x

% of 11B isotope =100-x

putting in the formula

Percentage of 11B= 100-25.37= 74.63%

the product of the pressure and volume is also constant

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.