Consider the following information. the lattice energy of cscl is δ h lattice = − 657 kj/mol. the enthalpy of sublimation of cs is δ h sub = 76.5 kj/mol. the first ionization energy of cs is ie 1 = 376 kj/mol. the electron affinity of cl is δ h ea = − 349 kj/mol. the bond energy of cl 2 is be = 243 kj/mol. determine the enthalpy of formation, δ h f , for cscl ( s ) .

-310.5 kJ/mol

Explanation:

The CsCl(s) will be formed by steps:

The enthanlpy of formation is the sum of all the energies involved in the steps:

ΔHf = 76.5 + 376 -349 + 243 -657

ΔHf = -310.5 kJ/mol

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).