How many aluminum atoms are in 2.58 grams of aluminum

5.75x10^22 atoms

Explanation:

From a clear understanding of Avogadro's hypothesis, we discovered that 1mole of any substance contains 6.02x10^23 atoms. This implies that 1mole of Al also contains 6.02x10^23 atoms.

1mole of Al = 27g

If 27g of Al contains 6.02x10^23 atoms, then 2.58g of Al will contain = (2.58 x 6.02x10^23)/27 = 5.75x10^22 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.

law of conservation of matter