Calculate the average atomic mass of boron (B), which has two isotopes: B-10 with 19.9% natural abundance, and B-11 with 80.1% abundance. Average atomic mass of boron = (f1)(M1) + (f2)(M2) Question 13 options: 12.1 amu 10.8 amu 9.2 amu 3.3 amu

The average atomic mass of boron is found to be  

10.80

Explanation:

also u answered it urself

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.