How many moles of potassium are in 3.78 x 10^21 atoms of K?

6.3 x 10^-3 moles

Explanation:

Based on Avogadro's law:

1 mole of any substance has 6.02 x 10^23 atoms

So, 1 mole of potassium = 6.02 x 10^23 atoms

Z moles = 3.78 x 10^21 atoms

To get the value of Z, we cross multiply:

(3.78 x 10^21 atoms x 1mole) = (6.02 x 10^23 atoms x Z moles)

3.78 x 10^21 = (6.02 x 10^23 x Z)

Z = (3.78 x 10^21) ➗ (6.02 x 10^23)

Z = 0.63 x 10^-2)

Place the result in standard form

Hence, Z = 6.3 x 10^-3 moles

Thus, there are 6.3 x 10^-3 moles of potassium in 3.78 x 10^21 atoms of K.

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.

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