Calculate the density of helium if a balloon with a capacity of 5.00 L holds 0.890 g.

Explanation:

Density is m/V. Also, 1 liter = 1000 . So, we get 0.890/(5*1000) = g/cm^3. You can convert this to kg/m^3 as well by multiplying it by 10. Depends which one you want.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.