Po−218 is an alpha emitter with a half-life of 3.0 minutes. if a sample contains 59 mg of po−218, how many alpha emissions would occur in 9.0 minutes?

1.4x10^20 alpha emissions. First, determine how many atoms of Po-218 you have. Do this by dividing the mass by 218 to get the number of moles, then multiply by Avogadro's number: 0.059 g / 218 g/mol * 6.0221409x10^23 atoms/mol = 1.63x10^20 atoms. Now we need to figure out how many half lives we're going to be observing the polonium. So take the time that we'll be observing and divide by the half life. So 9.0 / 3.0 = 3.0 So we're going to be spending 3 half lives. That means that only 2^-3, or 0.125 = 12.5 percent of the original polonium will be left. Which means that 100% - 12.5% = 87.5% of the atoms will have decayed. So let's figure that out. 0.875 * 1.63x10^20 = 1.43x10^20 Rounding to 2 significant figures gives 1.4x10^20 alpha emissions.

Thermohaline circulation and gyres

Standing in the sunlight and feeling the heat on your face (uv radiation is entering the skin, converting to infrared radiation, and is absorbed by your tissues)orstanding near a fire and feeling the heat on your skin (infrared radiation transfer)