Question

why does carbon, a nonmetal, tend to form covalent bonds rather than ionic bonds?
it has a very low electronegativity, making it easy to lose electrons.
its small size prevents it from participating in electron sharing.
sharing electrons allows carbon to form giant structures like diamond, graphite
it requires gaining or losing four electrons, which is energetically unfavorable for ion formation.
which of the following combinations would result in the formation of a precipitate?
acetic acid and potassium hydroxide solutions
magnesium nitrate and sodium sulfide solutions
sulfuric acid and barium hydroxide solutions
none of them

Explanation:

First Question (Carbon Bonding)

• Carbon has 4 valence electrons. To form an ion, it would need to gain or lose 4 electrons. Gaining 4 electrons (to fill its outer shell) or losing 4 electrons (to empty its outer shell) requires a large amount of energy, making ionic bond formation energetically unfavorable. Covalent bonding (sharing electrons) is a more energy - efficient way for carbon to achieve a stable electron configuration. The first option is wrong because carbon has a moderate electronegativity, not very low. The second option is wrong as carbon's size actually allows it to participate in electron sharing (e.g., in diamond and graphite structures). The third option is incorrect because the formation of giant structures is a result of covalent bonding, not the reason for covalent bonding.

Second Question (Precipitate Formation)

1. Magnesium nitrate ($\ce{Mg(NO_{3})_{2}}$) and sodium sulfide ($\ce{Na_{2}S}$) solutions:

• The reaction is $\ce{Mg(NO_{3})_{2}(aq) + Na_{2}S(aq)

ightarrow MgS(s) + 2NaNO_{3}(aq)}$. Magnesium sulfide ($\ce{MgS}$) is insoluble in water and will form a precipitate.

1. Sulfuric acid ($\ce{H_{2}SO_{4}}$) and barium hydroxide ($\ce{Ba(OH)_{2}}$) solutions:

• The reaction is $\ce{H_{2}SO_{4}(aq) + Ba(OH)_{2}(aq)

ightarrow BaSO_{4}(s) + 2H_{2}O(l)}$. Barium sulfate ($\ce{BaSO_{4}}$) is a well - known insoluble compound and will precipitate out.

1. Acetic acid and potassium hydroxide solutions:

• The reaction is $\ce{CH_{3}COOH(aq) + KOH(aq)

ightarrow CH_{3}COOK(aq) + H_{2}O(l)}$. Potassium acetate ($\ce{CH_{3}COOK}$) is soluble in water, so no precipitate forms.

Answer:

It requires gaining or losing four electrons, which is energetically unfavorable for ion formation.