What is the volume of 0.2 moles of neon gas at stp?

4.5 L

Explanation: Ideal gas at STP standard temperature and pressure: at STP

P = 1 atm

T = 1 °C convert to K (273 K)

Solution:

PV= nRT

Derive the equation to find V

V= nRT / P

Substitute the values

V= 0.2 moles x 0.082 L.atm/ mol. K x 273 K / 1 atm

Cancel out the units of moles, atm and K so the remaining uni is in L.

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.