If a original sample of radioactive uranium-238 had a mass of 400 grams, what is the total amount of the uranium-238 sample that would be left after 9 billion years?

What is the composition, in atom percent, of an alloy that consists of 4.5 wt% pb and 95.5 wt% sn? the atomic weights for pb and sn are 207.19 g/mol and 118.71 g/mol, respectively.(a) 2.6 at% pb and 97.4 at% sn(b) 7.6 at% pb and 92.4 at% sn(c)97.4 at% pb and 2.6 at% sn(d) 92.4 at% pb and 7.6 at% sn

How many moles is 14.5 cm^3 of platinum? the density of platinum is 21.45 g/cm^3.

What type of organic molecule comprises the majority of a potato?