What is the atomic mass of an element if 4.00 grams of it contains 2.98x10^22 atoms

The molar mass of the element is 80.8 g/mol

Explanation:

We are given:

Number of atoms =

According to mole concept:

number of atoms are contained in 1 mole of an element

So, number of atoms will be contained in of an element

To calculate the molar mass for given number of moles, we use the equation:

Given mass of element = 4.00 g

Moles of an element = 0.0495 moles

Putting values in above equation, we get:

Hence, the molar mass of the element is 80.8 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.