Construct a Born–Haber cycle for the formation of the hypothetical compound NaCl2, where the sodium ion has a 2+ charge (the second ionization energy for sodium is given in Table 7.2). (a) How large would the lattice energy need to be for the formation of NaCl2 to be exothermic?

Video transcript

Hi everyone here we have a question asking us how large must the lattice energy be for the formation of a hypothetical compound magnesium bromide. The magnesium having an charge of three plus to be exact thermic. So the entropy of formation a magnesium chloride solid equals the negative change in entropy of lattice. A magnesium chloride plus the change in entropy of formation of magnesium gashes Plus three times the change in entropy of formation of brown mean, gashes plus the first ionization energy of magnesium plus the second ionization energy of magnesium plus the third ionization energy of magnesium Plus three times the energy of browning. Now let's see what these values are. So the change an entropy of formation of magnesium gashes Is 147 .1 Killed Jules Per Mole. The change in entropy of formation of bro mean, gashes Is 111.9 kg per mole. The first ionization energy of magnesium is 738 kg joules per mole. The second ionization energy of magnesium Is 1451 kg per mole. The 3rd Ionization Energy of Magnesium Is 7733 killed joules per mole. And the energy of bro mean is 325 zero killed joules per mole. Now let's add this up. So the change in entropy a formation for magnesium chloride solid equals negative. The change in entropy of the lattice a magnesium chloride plus 147 . killed joules per mole plus three times .9 kg per mole plus 700 38 killed jules per mole Plus 1451 killed, joules per mole plus 733 killed, joules per mole plus three times -325 zero killed jules per mole. So the change in entropy of the formation of magnesium chloride equals negative. The change in entropy for the lattice of magnesium chloride plus 9429.8 kg joules per mole. So the change in entropy of formation of magnesium chloride should be negative to be exact thermic. So the change in entropy of the lattice of magnesium chloride must be greater than 29.8 killed groups per mole. And that is our final answer. Thank you for watching. Bye.