How many atoms of iron are in 0.750 moles of the compound
iron(iii) oxide?

2.26 × 10²⁴ atoms

Explanation:

In 1 mole of Fe₂O₃ (Iron(III) oxide), there are 6.02 × 10²³ molecules of Fe₂O₃ (Avogadro's number). The molecules of Fe₂O₃ in 0.750 moles are:

0.750 mol × (6.02 × 10²³ molecules/ 1 mol) = 4.52 × 10²³ molecules

In 1 molecule of Fe₂O₃, there are 5 atoms (2 atoms of Fe and 3 atoms of O). The atoms in 4.52 × 10²³ molecules of Fe₂O₃ are:

4.52 × 10²³ molecule × (5 atom/1 molecule) = 2.26 × 10²⁴ atom

There are 2.26 × 10²⁴ atoms in 0.750 moles of Fe₂O₃.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.