Answer:
1.673*10^-23 grams
Explanation:
This is a bit of an odd question, and can be done a few different ways.
In a "typical" NH3 molecule, N has 7 protons, and 7 neutrons, while H has 1 proton and 0 neutrons. In total in a NH3 molecule, there are 7+3*1 = 10 protons. We know how much a proton weighs, so we can directly multiple 10 by 1.673*10^-24 grams, getting 1.673*10^-23 grams
A more complicated way, in the case that a proton's mass isn't already given
If we don't know the mass of a proton, we can still do this problem. Most of the mass of a molecule resides in the protons and neutrons. a mole of ammonia that is made of N-14 and H-1 (numbers signifying atomic mass) weighs 14+3*1 = 17 grams. there are 6.022*10^23 molecules in a mol of any molecule, 17 grams of the specific ammonia that we have equals to 6.022*10^23 molecules.
6.022*10^23 molecules / mol = 17 grams / mol
6.022*10^23 molecules = 17 grams
1 molecule = 2.823*10^-23 grams
There are 10 protons and 7 neutrons in one molecule NH3, so if we subtract the mass of the neutrons in one molecule of NH3, we get the mass of the protons in one molecule of NH3
(mass of 10 protons + mass of 7 neutrons) - (mass of 7 neutrons) = mass of 10 protons
(mass of one NH3) - (mass of 7 neutrons) = mass of 10 protons
7 neutrons weigh 1.1725*10^-23 grams and 1 molecule of NH3 is 2.823*10^-23 grams so substitute everything
2.823*10^-23 - 1.1725*10^-23 = 1.6505e-23 grams, which is a fairly close value to what we got using the first method.
