Question

The increasing order of basic strength of \(\mathrm{Cl}, \mathrm{CO}_{3}^{2}\), \(\mathrm{CH}_{3} \mathrm{COO}, \mathrm{OH}, \mathrm{F}\) is (1) \(\mathrm{Cl}<\mathrm{F}<\mathrm{CH}_{3} \mathrm{COO}<\mathrm{CO}_{3}^{2}<\mathrm{OH}\) (2) \(\mathrm{Cl}^{-}<\mathrm{F}^{-}<\mathrm{CO}_{3}^{2-}<\mathrm{CH}_{3} \mathrm{COO}^{-}<\mathrm{OH}^{-}\) (3) \(\mathrm{CHI}_{3} \mathrm{COO}<\mathrm{Cl}<\mathrm{F}<\mathrm{CO}_{3}^{2}<\mathrm{OH}\) (4) \(\mathrm{F}<\mathrm{CO}_{3}^{2}<\mathrm{Cl}<\mathrm{CII}_{3} \mathrm{COO}<\mathrm{OII}\)

Short answer

Option (1)

Step-by-step solution

- Identify the basic species

The species given are \(\mathrm{Cl}^-\), \(\mathrm{CO}_{3}^{2-}\), \(\mathrm{CH}_{3}\mathrm{COO}^-\), \(\mathrm{OH}^-\), and \(\mathrm{F}^-\). We need to arrange these species in increasing order of their basic strength.

- Consider periodic trends

In general, the basicity of halide ions (e.g., \(\mathrm{Cl}^- \) and \(\mathrm{F}^-\)) decreases down the group in the periodic table. Hence, \(\mathrm{F}^-\) is less basic than \(\mathrm{Cl}^-\).

- Analyze other ions

Hydroxide ion (\(\mathrm{OH}^-\)) is a very strong base. The carbonate ion (\(\mathrm{CO}_{3}^{2-}\)) and acetate ion (\(\mathrm{CH}_{3}\mathrm{COO}^-\)) are also bases, but weaker than \(\mathrm{OH}^-\). Generally, \(\mathrm{CO}_{3}^{2-}\) is more basic than \(\mathrm{CH}_{3}\mathrm{COO}^-\).

- Arrange in increasing order

From the observations: \(\mathrm{Cl}^- < \mathrm{F}^- < \mathrm{CH_3COO}^- < \mathrm{CO_3^{2-}} < \mathrm{OH}^-\).

- Select the correct option

Comparing the arranged order with the given options, the correct increasing order of basic strength is:Option (1)

Key concepts

periodic trends

Periodic trends refer to patterns observed in the periodic table of elements. These trends can predict the behavior and properties of elements. One important trend is the change in basicity of halide ions (like \( \mathrm{Cl}^- \) and \( \mathrm{F}^- \)) down a group. As you move down the group, ions become less basic. This happens because larger ions have their charge spread over a larger area, making them less effective at donating electrons. Thus, \( \mathrm{F}^- \) (fluoride) is less basic than \( \mathrm{Cl}^- \) (chloride). Periodic trends help us understand these regular patterns effectively.

basicity of halides

Halide ions, such as fluoride (\( \mathrm{F}^- \)) and chloride (\( \mathrm{Cl}^- \)), show varying degrees of basicity. Basicity refers to an ion's ability to accept protons. Fluoride, being higher up in the periodic table, is smaller and more electronegative. This makes it hold onto its electrons tightly, thus less likely to accept protons, making it a weaker base compared to chloride. Chloride’s larger size and lower electronegativity allow it to be a bit more basic than fluoride. To summarize:

• The smaller the ion, the weaker the base (in halides).
• \( \mathrm{F}^- \) is less basic than \( \mathrm{Cl}^- \).

strong bases

A strong base is an ion or molecule that can accept protons very easily. Among the given species, hydroxide ion (\( \mathrm{OH}^- \)) is a very strong base. It readily accepts a proton to form water. This strong basicity is due to the presence of a lone pair of electrons on oxygen that is highly available for proton acceptance. Consequently, \( \mathrm{OH}^- \) outperforms other bases such as carbonate ion (\( \mathrm{CO_3^{2-}} \)) and acetate ion (\( \mathrm{CH_3COO}^- \)). This makes \( \mathrm{OH}^- \) the strongest base among the given ions.

carbonate ion

The carbonate ion (\( \mathrm{CO_3^{2-}} \)) is a moderately strong base. It can accept protons to form bicarbonate (\( \mathrm{HCO_3^-} \)). Carbonate’s basicity is largely due to its resonance structures, which delocalize the negative charge over multiple oxygen atoms. This resonance stabilization makes \( \mathrm{CO_3^{2-}} \) a weaker base than \( \mathrm{OH}^- \) but stronger than acetate ion (\( \mathrm{CH_3COO}^- \)). In terms of basicity among common ions:

• \( \mathrm{CO_3^{2-}} \) is more basic than \( \mathrm{CH_3COO}^- \).
• \( \mathrm{CO_3^{2-}} \) is less basic than \( \mathrm{OH}^- \).

acetate ion

The acetate ion (\( \mathrm{CH_3COO}^- \)) is a relatively weak base. It originates from acetic acid (\( \mathrm{CH_3COOH} \)), a weak acid. The ability of acetate to accept a proton is not very strong due to its resonance stabilization. In acetate, the negative charge is shared between two oxygen atoms, reducing its availability to accept protons. In comparison to other given species:

• \( \mathrm{CH_3COO}^- \) is less basic than \( \mathrm{CO_3^{2-}} \) and \( \mathrm{OH}^- \).
• It is more basic than \( \mathrm{F}^- \) and \( \mathrm{Cl}^- \).