Question about the molar mass....can you explain this...?

The comparative atomic masses (listed in the Periodic Table of the Elements) were developed by comparing equal volumes of different gases at the same temperature and pressure that were assumed to contain the same number of molecules. In the beginning, it was found that an atom of hydrogen was the smallest atom with the smallest mass. Every other atom's mass was compared to a mass of a hydrogen atom. The mass of one hydrogen atom was given the mass of 1 atomic mass unit (amu or μ), while a helium atom was found to have a mass of 4 atomic mass units, and so on. An atomic mass unit is equal to 1.6606 × 10^-24 g. One atom of hydrogen is too small to be useful, so scientists discovered another way to count atoms, using moles. A mole of hydrogen atoms equals 6.0221 × 10^23 atoms. So, if 1 hydrogen atom = 1.6606 × 10^-24 g Multiplying both sides of the above equation by Avogadro's Number gives: 6.0221 × 10^23 hydrogen atoms = (6.0221 × 10^23)(1.6606 × 10^-24 g) 6.0221 × 10^23 hydrogen atoms = 10.000299 × 10^-1 g 6.0221 × 10^23 hydrogen atoms ≈ 1 g or 1 mole of hydrogen atoms ≈ 1 g One mole of hydrogen atoms is a useful quantity. Note that simply looking up the atomic mass of hydrogen and expressing it in grams, we can find the mass of one mole of hydrogen atoms. Likewise, we can take any symbol or any formula for any substance and express its atomic or formula mass in grams, and we either have a mole of atoms or a mole of formula masses or molecules of any substance. For example, a mole of water molecules can be determined by adding up the atomic masses of two hydrogen atoms and one oxygen atom (1 amu + 1 amu + 16 amu = 18 amu). Simply measuring out 18 grams of water will give us approximately 1 mole (or 6.0221 × 10^23) of water molecules. While one molecule of water is rather insignificant as far as we are concerned, one mole of water molecules can be swallowed in a single gulp and relieve thirst for a little while. P.S.: Later on, with the discovery of isotopes, scientists found it more accurate to define 1 amu as 1/12 of the mass of C-12 atom.

A molar pregnancy happens when there are certain abnormalities in the fertilized egg at conception. The fertilized egg either never develops into an embryo (this is called a complete mole) or it develops abnormally and can't survive (this is a partial mole). In normal pregnancies, the fertilized egg contains 23 chromosomes from the father and 23 from the mother. In most complete molar pregnancies, the fertilized egg contributes no maternal chromosomes and the chromosomes from the father's sperm are duplicated, so you end up with two copies of chromosomes from the father and none from the mother. In this case, there's no embryo, amniotic sac, or any normal placental tissue. Instead, the placenta forms a mass of cysts that looks like a cluster of grapes. In most partial molar pregnancies, the fertilized egg has the normal complement of chromosomes from the mother but double the chromosomes from the father, so there are 69 chromosomes instead of the normal 46. (That can happen when chromosomes from the sperm are duplicated or when two sperm fertilize the same egg.) In this case, there's some normal placental tissue among the cluster-like mass of abnormal tissue. The embryo does begin to develop, so there may be a fetus, or just some fetal tissue, or an amniotic sac. But even if a fetus is present, in most cases it's so abnormal that it can't survive. It can be scary and sad to lose a pregnancy this way. But as long as you get proper treatment, you're unlikely to have any long-term physical consequences. FOR THE PEOPLE THAT COPIED MY ANSWER....... GET A LIFE!!