Was the periodic table of elements created at once by one scientist yes or no

Yes

Explanation:

It was Dmitri Mendeleev, a Russian chemist and teacher.

No, it wasn't. On Feb.17 in 1869, a very intelligent Russian professor of chemistry, Dimitri Ivanovich Mendeleev created his first part of the periodic table. I hope that helps you.

Explanation:

i think so it’s will be b yes i believe its

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%