Solution Concentration and Characteristics of Salt Solution
The concentration of the solution states quantitatively the composition of the solute and the solvent in the solution. Concentrations are generally expressed in terms of the ratio of the amount of solute to the amount of solvent. Examples of several units of concentration are molar, molal, and parts per million (parts per million).
Characteristics of Salt Solution
If an acidic solution with an alkaline solution is reacted, the H + ion (from acid) will react with the OH- ion (from the base) to form water. This reaction between acids and bases is called a neutralization reaction if the amount of acid is equal to the amount of base. So called because in addition to water, also produced a neutral substance that is salt, if the amount of acid and the amount of base have the same ratio. This reaction is also known as the salting reaction because it produces salt.
Salt is in the form of neutral salt, basic salt and acid salt. Generally salt dissolves easily in water, is a solid at room temperature (25oC), is an electrolyte so that it can conduct electric current, has a high boiling point and melting point.
The characteristics of salt include:
usually occurs from the reaction between acids and bases
acidic when formed from strong acids and weak bases
basic if formed from weak acids and strong bases
neutral when formed from strong acids and strong bases or weak acids and weak bases.
Type of Salt Solution
Salt consists of 4 types
Formed from strong acids and strong bases, are neutral for example NaCl, K2SO4
Formed from strong acids and weak bases, are acidic, for example NH4Cl and
Al2 (SO4) 3
Formed from weak acids and strong bases, are alkaline, for example
CH3COONa, HCOOK, Na2CO3
Formed from weak acids and weak bases, their properties depend on the value of Ka and Kb, for example (NH4) 2CO3
Salts derived from strong acids and strong bases do not undergo hydrolysis. pH = 7
Salts derived from weak acids and strong bases only experience partial hydrolysis in water.
Salt formula
Type of Salt Solution
Types of Salt Can Be Hydrolyzed, Salt consists of four types, which are divided based on the acid-base components that make up HYDROLYSIS
1. Salt from Strong Acid with Strong Base
Strong acids and strong bases react to form salt and water. Salt cations and anions come from strong electrolytes that are not hydrolyzed, so this solution is neutral, the pH of this solution is equal to 7.
Example: NaCl Salt
In water, perfect ionized NaCl forms Na + and Cl- ions
NaCl (aq) Na + (aq) + Cl- (aq)
The Na + ion comes from strong acids and the Cl- ion comes from strong bases so that they don't react with water.
Na + (aq) + H2O (l) (no reaction)
Cl- (aq) + H2O (l) (no reaction)
Therefore, the solution remains neutral (pH = 7).
2. Salt from Strong Acid with Weak Base
Salts formed from strong acids with weak bases undergo partial (partial) hydrolysis in water. This salt contains acid cations that undergo hydrolysis. This salt solution is acidic, pH <7.
Example
Calculates the pH of an acidic salt solution
Examples of salt solutions that are acidic are NH4Cl, NH4Br, Al2 (SO4) 3.
Consider the following hydrolysis reaction!
NH4 + (aq) + H2O (l) NH4OH (aq) + H + (aq)
The hydrolysis reaction is an equilibrium reaction. Although only a little of the salt undergoes a hydrolysis reaction, it is enough to change the pH of the solution. The equilibrium constant of the hydrolysis reaction is called the hydrolysis constant and is denoted by Kh.
Kh = [NH4OH] [H +] / [NH4 +]
H2O is ignored because H2O is constant. NH4OH is always the same as [H +] so
Salt from Strong Acid
3. Salt from Weak Acid with Strong Base
Salts formed from weak acids with strong bases undergo partial hydrolysis in water. This salt contains alkaline anions which undergo hydrolysis. This salt solution is alkaline (pH> 7).
This salt is ionized in water to produce ions. Cations are from strong bases and Anions are from weak acids. Example: CH3COONa, NaF, CH3COOK, HCOOK
Example: CH3COOBa salt
Calculates the pH of a salt solution that is Alkaline
Consider the CH3COO-hydrolysis reaction from the following CH3COOBa salt!
CH3COO- + H2O CH3COOH + OH-
The equilibrium constant of the hydrolysis reaction is called the hydrolysis constant which is denoted Kh