From the given salt solution systems, the X − ion that has the weakest conjugate acidand the decreasing order of the basic strength of the given anions, is to be determined. Concept introduction: A salt is a strong electrolyte, which dissociates completely when added to water. When a salt contains an anion that comes from a weak acid then the anion recombines with water to produce a weak acid and hydroxide ions, and forms a basic solution. The cation, if it comes from a strong base, does not recombine and is present in the solution as a free ion without having any effect on the pH of the solution. The reaction of the salt ( BA ) which takes place is: A − ( aq ) + H 2 O ( l ) ⇌ HA ( aq ) + OH − ( aq ) Here, A − comes from the weak acid HA and B + comes from strong base BOH . The pH of this solution is determined by the [ OH − ] The relationship between K b , K a and K w gives the quantitative basis of the reciprocal relationship between the strength of an acid and its conjugate base or vice-versa. K a × K b = K w …… (1) K b is the measure of dissociation of a base and is known as the base-ionization constant, which is specific at a particular temperature. K b = [ OH − ] [ HA ] [ A − ] …… (2)
From the given salt solution systems, the X − ion that has the weakest conjugate acidand the decreasing order of the basic strength of the given anions, is to be determined. Concept introduction: A salt is a strong electrolyte, which dissociates completely when added to water. When a salt contains an anion that comes from a weak acid then the anion recombines with water to produce a weak acid and hydroxide ions, and forms a basic solution. The cation, if it comes from a strong base, does not recombine and is present in the solution as a free ion without having any effect on the pH of the solution. The reaction of the salt ( BA ) which takes place is: A − ( aq ) + H 2 O ( l ) ⇌ HA ( aq ) + OH − ( aq ) Here, A − comes from the weak acid HA and B + comes from strong base BOH . The pH of this solution is determined by the [ OH − ] The relationship between K b , K a and K w gives the quantitative basis of the reciprocal relationship between the strength of an acid and its conjugate base or vice-versa. K a × K b = K w …… (1) K b is the measure of dissociation of a base and is known as the base-ionization constant, which is specific at a particular temperature. K b = [ OH − ] [ HA ] [ A − ] …… (2)
Solution Summary: The author explains the relationship between the strength of an acid and its conjugate base or vice-versa.
From the given salt solution systems, the X− ion that has the weakest conjugate acidand the decreasing order of the basic strength of the given anions, is to be determined.
Concept introduction:
A salt is a strong electrolyte, which dissociates completely when added to water.
When a salt contains an anion that comes from a weak acid then the anion recombines with water to produce a weak acid and hydroxide ions, and forms a basic solution. The cation, if it comes from a strong base, does not recombine and is present in the solution as a free ion without having any effect on the pH of the solution.
The reaction of the salt (BA) which takes place is:
A−(aq)+H2O(l)⇌HA(aq)+OH−(aq)
Here, A− comes from the weak acid HA and B+ comes from strong base BOH. The pH of this solution is determined by the [OH−]
The relationship between Kb, Ka and Kw gives the quantitative basis of the reciprocal relationship between the strength of an acid and its conjugate base or vice-versa.
Ka×Kb=Kw …… (1)
Kb is the measure of dissociation of a base and is known as the base-ionization constant, which is specific at a particular temperature.
7 (a) Describe what happens when each of the following molecules is
separately dissolved in water and illustrate with an equation in each
case:
(i) ethanoic acid (CH₂COOH)
(ii) ammonia (NH3)
(b) Identify the conjugate acids and bases in the substances mentioned
in question 7(a) above.
(c) Explain the difference between: (i) a strong acid and weak acid and
(ii) a strong base and a weak base
Sodium hypochlorite solution is also known as bleach. It contains the hypochlorite ion ClO-.
(a) Write an equation for the reaction between hypochlorite ion and ammonium ion. Label the acids and bases in the forward and reverse reactions. Identify the two conjugate acid-base pairs.
(b) This equilibrium favors the reactants. Which of the acids is stronger and donates protons more readily?
(a) Describe what happens when each of the following molecules is separately dissolved in water and illustrate with an equation in each case:
ethanoic acid (CH3COOH)
ammonia (NH3)
(b) Identify the conjugate acids and bases in the substances mentioned in question 7(a) above.
(c) Explain the difference between: (i) a strong acid and weak acid and (ii) a strong base and a weak base
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