Which of the following correctly identifies which has the higher first ionization energy, ci or ar, and supplies the best justification? a. cl, because of its higher electronegativity b. cl, because of its higher electron affinity c. ar, because of its completely filled valence shell d. ar, because of its higher effective nuclear charge given the information in a table of bond dissociation energies, calculate the change in enthalpy, delta h, in units of kj, for the following gas-phase reaction: h_2c = ch_2 + h-br rightarrow ch_3ch_2br a. +148 b. -148 c. +200 d. -200

d. Ar, because of its higher effective nuclear charge

For the secon part see explanation below.

Explanation:

The first ionization energy is the energy required to remove an electron from the atom from its outermost shell. It depends on the nuclear charge, distance from the nucleus and the screening of other electrons in the inner shells of the atom.

Comparing Cl and Ar we see that being both elements of the third period, the Ar atom has one more proton than Cl and therefore the electron feels more nuclear charge making the first ionization of Ar greater than Cl.

a) False, electronegativity relates to attraction for an electron and not to the first ionization.

b) False, again electron affinity is not first ionization, it is defined as the energy released when the atom captures an added electron.

c) False,athough it is true that Ar has  a complete octet, the higher first ionization is affected by nuclear charge. The screening of electrons in the n= 1 and 2 shells is almost the same so what is important is that the electrons in the n= 3 shell feel more nuclear charge.

d) True for all the reasons given previously : the higher effective nuclear charge in Ar.

For the second part, we have to make an inventory of the bonds being broken and formed:

ΔHºrxn = H broken - H formed, where H is the bond energy

H2 C = CH_2  +   H-Br    ⇒   CH_3CH_2Br

ΔHºrxn  = ( 1 C=C + 4 C-H + 1 H-Br)   -   ( 1 C-C + 5 C-H + 1 C-Br)

ΔHºrxn (kJ) =  (614 + 4(413) + 363) - ( 347 + 5 (413) + 276)

ΔHºrxn (kJ) = 2629 -  2688 =  -59 kJ

This value is not in the choices due to mistaken bond energy values from the tables.

the answer is c

tell me if wrong

i think is conclusions.i think so