Answer:
The mass of 1.26 mole of water, H₂O, is 22.68 grams
Explanation:
Molar mass is the amount of mass that a substance contains in one mole. In other words, the molar mass of an atom or a molecule is the mass of one mole of that particle and its unit is g/mole.
In this case, being:
the molar mass of water H₂O is:
H₂O= 2*1 g/mole + 16 g/mole= 18 g/mole
Then you can apply the following rule of three: if 18 grams are present in 1 mole of H2O, how much mass is present in 1.26 moles of water?

mass= 22.68 grams
<u><em>The mass of 1.26 mole of water, H₂O, is 22.68 grams</em></u>
Answer:
The hydrogen atom has just one electron, but many spectral lines. However it contains many shells and the movement of that electron from one shell to another causes the release of energy and also an emission of photons.
A spectral line are dark or bright lines formed within a specific frequency range which differ from other frequencies.Because of the difference of energy for the various shells, it produces different wavelengths and this is the reason for the many spectral line for hydrogen.
Its arbitrary. It was developed on the greek phoenetic system and never reallybwas explained.