Question

write the meaning and examples of strong and weak acid, base and alkali.​

Answer 1

Answer:

Except for their names and formulas, so far we have treated all acids as equals, especially in a chemical reaction. However, acids can be very different in a very important way. Consider HCl(aq). When HCl is dissolved in H2O, it completely dissociates into H+(aq) and Cl−(aq) ions; all the HCl molecules become ions:

HCl → H+(aq) + Cl−(aq) (100%)

Any acid that dissociates 100% into ions is called a strong acid. If it does not dissociate 100%, it is a weak acid. HC2H3O2 is an example of a weak acid:

HC2H3O2→ H+(aq) + C2H3O2−(aq) (~5%)

Because this reaction does not go 100% to completion, it is more appropriate to write it as an equilibrium:

HC2H3O2 ⇄ H+(aq) + C2H3O2−(aq)

As it turns out, there are very few strong acids, which are given in Table 12.2 “Strong Acids and Bases”. If an acid is not listed here, it is a weak acid. It may be 1% ionized or 99% ionized, but it is still classified as a weak acid.

The issue is similar with bases: a strong base is a base that is 100% ionized in solution. If it is less than 100% ionized in solution, it is a weak base. There are very few strong bases (see Table 12.2 “Strong Acids and Bases”); any base not listed is a weak base. All strong bases are OH– compounds. So a base based on some other mechanism, such as NH3 (which does not contain OH− ions as part of its formula), will be a weak base.

Table 12.2 Strong Acids and Bases

Acids Bases

HCl LiOH

HBr NaOH

HI KOH

HNO3 RbOH

H2SO4 CsOH

HClO3 Mg(OH)2

HClO4 Ca(OH)2

Sr(OH)2

Ba(OH)2

Example 6

Identify each acid or base as strong or weak.

HCl

Mg(OH)2

C5H5N

Solution

Because HCl is listed in Table 12.2 “Strong Acids and Bases”, it is a strong acid.

Because Mg(OH)2 is listed in Table 12.2 “Strong Acids and Bases”, it is a strong base.

The nitrogen in C5H5N would act as a proton acceptor and therefore can be considered a base, but because it does not contain an OH compound, it cannot be considered a strong base; it is a weak base.

Test Yourself

 

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Explanation:

Answer 2

Answer:

The most common strong acids and bases, and some examples of weak acids and bases, together with definition of strong and weak acids and bases

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