. 2. Which has more atoms: 2.5 mol of calcium carbonate, CaCO3, or 3.5 mol of calcium hydroxide, Ca(OH)2

Calcium hydroxide has more atoms.

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 one mole of said substance. Its value is 6.023*10²³ particles per mole. Avogadro's number applies to any substance.

Then you can apply the following rules of three:

amount of moles of calcium carbonate= 1.50575*10²⁴

amount of moles of calcium hydroxide= 2.10805*10²⁴

2.10805*10²⁴ is greater is 1.50575*10²⁴, so calcium hydroxide has more atoms.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.