How many moles are in 124.7 g of Ba(OH)2

0.73 mol

Explanation:

No. of moles(n)= Given mass/molar mass.

Given mass=124.7g

Molar mass of Ba(OH)2= Molar mass of (Barium+2Oxygen+2Hydrogen)=137+32+2=171g

No. of moles= 124.7g/171g=0.73 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.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.