one part of dalton's atomic theory states: compounds are formed by combinations of atoms from two or more elements. is this statement currently considered to be true or false and why?

The statement is considered to be true

Explanation:

The statement is true because when elements chemically combine, there are interactions between their valence electrons, causing the two elements to be bonded together to form what is known as a compound.

Compounds can only be formed from interactions between two or more elements. examples include:

Hydrogen + Oxygen = H2O (water)

Sodium + Chlorine = NaCl

Note that if atoms of the same element combine, what is formed is a molecule, not a compound. Some atoms usually do this to attain stability. examples include = O2 H2 and  N2. They are oxygen molecule, hydrogen molecule, and nitrogen molecule respectively.

Compounds are only formed when different elements combine to attain electronic stability.

what he said was true

Explanation: i wished that i could have said the same.

petroleum? coal maybe?

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%