C-12 and c-13 are naturally occurring isotopes of the element carbon. c-12 occurs 98.89% of the time and c-13 occurs 1.108% of the time. what calculation should be used to determine the atomic mass of this element?

We will determine the weighted average of the atomic mass of two isotopes.

Explanation:

The atomic mass of an element is the weighted average of atomic masses of the most abundant isotopes occur in nature.

Given:

Percentage abundance of C-12 : 98.89%

Percentage abundance of C-13: 1.108%

The atomic mass of carbon will be"

Atomic mass = g/mol

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.

i think it's letter a.