Ambrose
Chemistry Lab: Hydrolysis of Salts
Name_____________________________________________________Date__________________
New Concept: Hydrolysis Reactions
Review Concepts/Application: Writing chemical formulas, writing ionic equations, determining solubility, measuring acidity and basicity.
Pre-Lab Discussion
A salt is an ionic compound containing positive ions other than H+ and negative ions other than OH-. Most salts will dissociate to some degree when placed in water. In many cases, ions from the salt will react with water molecules to produce hydronium ions (H3O+) or hydroxide ions. Any chemical reaction in which water is one of the reactants is called a hydrolysis reaction.
Salts are generally formed from the neutralization reaction between an acid and a base. A salt formed from a strong acid and a strong base will not hydrolyze (react with water). When placed in water, these salts dissociate completely, and their ions remain uncombined in solution. An example of such a salt is NaCl, formed from a strong acid (HCl) and a strong base (NaOH).
Salts formed from a strong acid and a weak base hydrolyze to form a solution that is slightly acidic. In this kind of hydrolysis, the water molecules actually react with the cation from the weak base. For example, when ammonium chloride, NH4Cl, hydrolyzes, water molecules react with the NH4+ ion:
NH4+ + 2H2O ----------> NH4OH + H3O+
The formation of the H3O+ (hydronium) ion from this reaction makes the solution acidic.
Salts formed from a weak acid and a strong base hydrolyze to form a solution that is slightly basic. In this kind of hydrolysis, it is the anion from the weak acid that actually reacts with the water. For example, when sodium acetate, NaC2H3O2, hydrolyzes, water molecules react with the acetate ion:
C2H3O2- + H2O ---------> HC2H3O2 + OH-
The formation of the OH- ion from this reaction makes the solution basic.
Salts formed from a week
Name_____________________________________________________Date__________________
New Concept: Hydrolysis Reactions
Review Concepts/Application: Writing chemical formulas, writing ionic equations, determining solubility, measuring acidity and basicity.
Pre-Lab Discussion
A salt is an ionic compound containing positive ions other than H+ and negative ions other than OH-. Most salts will dissociate to some degree when placed in water. In many cases, ions from the salt will react with water molecules to produce hydronium ions (H3O+) or hydroxide ions. Any chemical reaction in which water is one of the reactants is called a hydrolysis reaction.
Salts are generally formed from the neutralization reaction between an acid and a base. A salt formed from a strong acid and a strong base will not hydrolyze (react with water). When placed in water, these salts dissociate completely, and their ions remain uncombined in solution. An example of such a salt is NaCl, formed from a strong acid (HCl) and a strong base (NaOH).
Salts formed from a strong acid and a weak base hydrolyze to form a solution that is slightly acidic. In this kind of hydrolysis, the water molecules actually react with the cation from the weak base. For example, when ammonium chloride, NH4Cl, hydrolyzes, water molecules react with the NH4+ ion:
NH4+ + 2H2O ----------> NH4OH + H3O+
The formation of the H3O+ (hydronium) ion from this reaction makes the solution acidic.
Salts formed from a weak acid and a strong base hydrolyze to form a solution that is slightly basic. In this kind of hydrolysis, it is the anion from the weak acid that actually reacts with the water. For example, when sodium acetate, NaC2H3O2, hydrolyzes, water molecules react with the acetate ion:
C2H3O2- + H2O ---------> HC2H3O2 + OH-
The formation of the OH- ion from this reaction makes the solution basic.
Salts formed from a week