Lithium forms compounds which are used in dry cells and storage batteries and in high-temperature lubricants. it has two naturally occurring isotopes, 6li (isotopic mass = 6.015121 amu) and 7li (isotopic mass = 7.016003 amu). lithium has an atomic mass of 6.9409 amu. what is the percent abundance of lithium-6?

The naturally occurring isotopes of Li are Li-6 of mass 6.015121 amu and Li-7 of mass 7.016003 amu. The atomic mass of Li is 6.9409 amu, the percent abundance can be calculated using the following relation.

Atomic mass=m(Li-6 )×%(Li-6 )+m(Li-7 )×%(Li-7 )

Let the percent abundance of Li-6 be X thus, that of Li-7 will be 1-X, putting the values,

Or,

Or,

X=0.075

Thus,

Thus, percent abundance of Li-6 is 0.075 or 7.5 % and that of Li-7 is 0.925 or 92.5%.

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.