What chemical reaction??? Very vague
Answer:
Electrons occupy orbitals with the lowest energy first.
Explanation:
The Aufbau Principle states that electrons will fill the atomic orbitals with the lowest energy levels first, before occupying others with higher energy levels.
For example, electrons will fill the 1s orbital before filling the 2s orbital.
Answer: There are 0.0637 moles present in 85.0 mL of 0.750 M KOH.
Explanation:
Given: Volume = 85.0 mL (1 mL = 0.001 L) = 0.085 L
Molarity = 0.750 M
It is known that molarity is the number of moles of solute present in liter of a solution.
Therefore, moles present in given solution are calculated as follows.

Thus, we can conclude that there are 0.0637 moles present in 85.0 mL of 0.750 M KOH.
Answer:
See Explanation
Explanation:
The way by which a metal is obtained from its ore is determined by the chemical reactivity of the metal.
Metals that are highly reactive are chiefly obtained by electrolysis of the metal salt. These metals are found high up in the metal activity series.
Metals that are at the middle of the series are moderately reactive and are obtained by electrolysis or by reduction since they still form ionic salts.
Metals that are far lower in the series can only be obtained by heating them in air because they are mostly unreactive.
Hence, moderately reactive metals at the middle of the series are not obtained by roasting in air.