A sample of polonium-210 has an initial mass of 390 milligrams (mg). If the half-life of polonium-210 is 36 days, how many mg of the sample remains after 36 days? A.
48.75 mg

B.
392 mg

C.
97.5 mg

D.
195 mg

Suppose a pair of chemical compounds a and b can react in two different ways: a + b -> c reaction 1 gives product c. a + b -> d reaction 2 gives product d. the following facts are known about the two reactions: . reaction 1 is endothermic and reaction 2 is exothermic. if a reaction vessel is charged (filled) with a and b , then at first d is produced faster than c. use these facts to sketch a qualitative reaction energy diagram for both reactions. note: because these sketches are only qualitative, the energies don? t have to be exact. they only have to have the right relationship to each other. for example, if one energy is less than another, that fact should be clear in your sketch.