How much energy is evolved when 2.65 mg of Cl(g) atoms adds electrons to give Cl1-(g) ions.
No clue how to go about solving this problem as it doesn't really relate to any of my examples in my text book or notes. All I can find that related to this problem is electron affinity and E=(K*Q1*Q2)/r where K is a constant. The EA for Cl is -349 kJ/mol. But I just cant find anything else out about this problem. Any help is great as I'm out of ideas.
What about delta Hfsup>o?
For the reaction Cl + e ==> Cl^-, you can look up delta Hof of Cl and for Cl^- and delta H rxn = delta H products - delta H reactants, then convert from mol to 2.65 mg. My text gives +121.7 kJ/mol for deltHof Cl and -226 for Cl^-. Of course that's just delta H; but you could do the same for delta Go.
@DrBob222 - I understand up to the part about the conversion of mol to 2.65 mg. I understand that the enthalpy change is 121.3 kJ/mol for Cl(g) and that would be the reactant part of the equation. But whats the deal with working with 2.65mg and the delta Go?
To solve this problem, you can use the concept of electron affinity, which is the energy released when an atom in the gas phase gains an electron to form a negatively charged ion.
First, convert the given mass of Cl(g) atoms into moles. To do this, use the molar mass of Cl, which is approximately 35.45 g/mol.
Mass of Cl(g) = 2.65 mg = 0.00265 g
Moles of Cl(g) = (0.00265 g) / (35.45 g/mol) ≈ 0.000075 mol
Since the question asks for the energy evolved when Cl(g) atoms gain electrons to form Cl1-(g) ions, we need to calculate the total energy evolved for the given number of moles.
The electron affinity (-349 kJ/mol) represents the energy released when one mole of Cl(g) atoms gains an electron. Therefore, the energy released for 0.000075 mol of Cl(g) atoms would be:
Energy released = (Electron affinity) × (Number of moles)
Energy released = (-349 kJ/mol) × (0.000075 mol)
Energy released ≈ -0.0262 kJ
Note that the negative sign indicates the release of energy during the process.
Therefore, approximately 0.0262 kJ of energy is evolved when 2.65 mg of Cl(g) atoms adds electrons to give Cl1-(g) ions.
The ionization (is always concerned with the formation of positive ions) of Chlorine is given by the following equation;
Cl --> Cl+ + e- IE = 1251.19 KJ/mol
While the electron affinity (is always concerned with the formation of negative ions) of Chlorine is given by the following equation;
Cl + e- --> Cl- EA = -349 kJ/mol
# moles of Cl = 0.00265 g/35.5 g/mol
= 0.0000746479 mol
Therefore, the energy involved in the reaction is E = EA x nCl
= -0.026 kJ
Exothermic reaction because the energy is released when the atom gains electrons