1. Which sample contains a total of 9.0 * 10 ^ 23 atoms ? A) 0.50 mole of HCI B) 0.75 mole of H 2 O C) 1.5 moles of Cu D) 1.5 moles of H 2

The sample that contains 9.0 x atoms would be 1.5 moles of Cu.

1 mole of a substance contains 6.0 x   atoms of the same substance. Thus:

Hence, the only sample that contains  9.0 x   atoms is 1.5 mole of Cu.

More on number of atoms of substances can be found here: link?

c. 1.5 moles of Cu will contain a total of 9.0 * 10 ^ 23 atoms.

Explanation:

To convert moles into atoms,  the molar amount and number of atom is multiplied by Avagadro's number.

Avagadro's number is 6.022×  

So applying the formula in the given sample:

A) 0.5×6.022×

   3.01× atoms.

B) 0.75 mole of H20

O.75×6.022×

= 4.5166×  atoms.

C) 1.5 moles of Cu

  1.5×6.022×

  =  9.033×

D). 1.5 moles of H2

1.5 × 2 × 6.022 ×

= 18.066 × atoms   because H2 is 2 moles of hydrogen.

Atom is the smallest entity of matter having property of the element to which it is a part.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

i belive it is water