Your teacher gives you a black powder. when you dissolve the powder in water, you see red particles that float to the top, black particles that sink to the bottom, and a green liquid.
what was the black powder?
compound
element
pure substance
mixture

Answer : The correct option is, mixture

Explanation :

Mixture : It is defined as the substance that is made by the combination of two or more different components.

Pure substance : It is defined as a substance that is made by the combination of only one type of atom or only one type of molecule.

Compound : It is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.

Element : It is a pure substance which is composed of atoms of similar elements.

According to the definition of mixture, black powder is a mixture because it is made by the combination of red particles that float to the top, black particles that sink to the bottom and a green color liquid.

Hence, the correct option is, mixture

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%