Answer:
5*10²⁴ chlorine atoms are found in 8.3 moles of chlorine.
Explanation:
Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023*10²³ particles per mole. Avogadro's number represents a quantity without an associated physical dimension, so it is considered a pure number that allows describing a physical characteristic without an explicit dimension or unit of expression. Avogadro's number applies to any substance.
Then you can apply the following rule of three: if 1 mole of the compound contains 6.023 * 10²³ atoms, 8.3 moles of the compound how many atoms does it have?

amount of atoms≅ 5*10²⁴ atoms
<u><em>5*10²⁴ chlorine atoms are found in 8.3 moles of chlorine.</em></u>
Full question need, post more
Answer: Compound
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water 

Thus as it give that the red sample on being heated, a gas is released and a blue powder is left after the heating. Thus the given sample is a compound.
I think it is decomposition because it processes in which chemical species break up into simpler parts.
<u>Answer:</u> The mass of water that should be added in 203.07 grams
<u>Explanation:</u>
To calculate the molality of solution, we use the equation:

Where,
m = molality of barium iodide solution = 0.175 m
= Given mass of solute (barium iodide) = 13.9 g
= Molar mass of solute (barium iodide) = 391.14 g/mol
= Mass of solvent (water) = ? g
Putting values in above equation, we get:

Hence, the mass of water that should be added in 203.07 grams