Solution : A neutralisation reaction is a chemical reaction between an acid and base dissolved in water. For example. Show A reaction of an acid with a base to form salt and water is a neutralization reaction.When an acid is mixed with a base, the acid and base neutralise each other’s effect and form salt and water. Since acid and base neutralize each other's effect,it is called neutralization reaction. For Example: When Sodium Hydroxide ( NaOH) , a base, reacts with Hydrochloric acid (HCl) , it forms the salt, Sodium Chloride (NaCl) and Water. Hint: The neutralization reaction is the one in which an acid reacts with an equimolar amount of base to give salt and water.The example could be a reaction between any strong acid and a base. The sodium chloride formed is a result of neutralization reaction. Complete step by step answer: Some of the examples of the neutralization reaction are as - Ex. 2:- The second reaction is the reaction of magnesium hydroxide with HCl. The magnesium hydroxide is also known as milk of magnesia and it dissociates as - Note: It must be noted that it is not mandatory for neutralization reaction to have a pH value of exact 7. It can be near to 7 also because during experiments, many other factors also need to be taken care of like temp, pressure and concentration to have the stable rate. Neutralization reaction is a very important class of chemical reaction in which the effect or activity of an acid is neutralized by a base and vice versa. The acid and base forms salt and water as the products of the reaction along with generation of heat. Neutralization reactions actually take place between the acidic proton from the acid and the hydroxyl group of the base to generate water( H+ and OH- react to form H2O). The concentrations of the acid and base are the determining factors for the volumes of the individual to be taken. Acid + Base \[\rightarrow\] Salt + Water For example, HCl + NaOH \[\rightarrow\] NaCl + H2O H2SO4 + NaOH \[\rightarrow\] Na (SO4)2 + H2O If the strengths are known, then we can find the volumes which will completely neutralize each other and vice versa. For this, we can use the formula, Volume (acid) \[\times\] concentration (H+ ions) = volume (base) \[\times\] concentration (OH− ions) Question If 10 ml of 0.5M HCl neutralizes 50ml of NaOH of unknown strength. Find its strength. Answer: 0.5 \[\times\] 10 = M of base \[\times\] 50 By cross multiplication, M of base = \[\frac{(0.5 \times 10)}{50} \] = \[\frac{5}{50} \] = 0.1 M Types of Neutralization ReactionsNow, there are four types of neutralization reactions: 1. Strong acid and strong base 2. Strong acid and weak base 3. Weak acid and strong base 4. Weak acid and weak base 1. Strong Acid and Strong Base Strong acids and strong bases dissociate entirely in aqueous conditions. For example, HCl, H2SO4 are strong acids and NaOH, KOH is a strong base. HCl (aq) \[\rightarrow\] H+ (aq) + Cl-(aq) NaOH (aq) \[\rightarrow\] Na+ (aq) + OH-(aq) H+ + OH- \[\rightarrow H_{2}O \] Na+ + Cl-\[\rightarrow\] NaCl The overall reaction is, HCl + NaOH \[\rightarrow\] NaCl + H2O When a strong acid neutralizes a strong base, the resultant is neutral because all the H+ ions react with all the OH-ions to form water. There are no surplus H+ or OH- ions present in the resultant solution. Its pH is 7. General reactions; Strong Acid: HA +H2O \[\rightarrow\] A- (aq) + H3O+ (aq) Strong Base: BOH + H2O \[\rightarrow\] B+ (aq) + OH-(aq) 2. Strong Acid and Weak Base Weak bases don’t dissociate only to about 5-10%. Here the amount of OH- ions is very less compared to the amount of H+ ions available. Therefore, the resultant solution is acidic. Its pH lies between 3-6. Weak Base: BOH + H2O \[\longleftrightarrow\] B+ (aq) + OH-(aq) (or) B + H2O \[\longleftrightarrow\] BH+ (aq) + OH-(aq) Examples of weak bases include Mg (OH)2, Ca (OH)2, and Ba (OH)2. \[K_b = \frac{OH^- B^+}{BOH}\] Taking log on both sides you get: \[Log K_b = log(\frac{OH^- B^+}{BOH} )\] Splitting the log terms: \[Log K_b = log OH^- + log (\frac{B^+}{BOH})\] Since pKb = -log10 Kb and pOH = -log10 [OH-], therefore: \[-pK_b = – pOH + log (\frac{B^+}{BOH})\] \[P_{OH} = pK_b + log (\frac{B^+}{BOH})\] This equation can also be written as: pOH = pKb + \[log (\frac{salt}{base})\] 3. Strong Base and Weak Acid Weak acids don’t dissociate entirely in aqueous conditions. The OH- ions concentration is much higher compared to the free H+ ions. Therefore, the resultant solution is basic with a pH of around 8-11. Weak acid: AH +H2O \[\longleftrightarrow\] A-(aq) + H3O+ (aq) Example of weak acids include; acetic acid and all the other organic acids. Following the law of dissociation, the acid dissociation constant Ka can be defined according to the equation as, \[Ka = \frac{H^+ A^-}{HA} \] Taking log on both sides you get: Log Ka = \[log (\frac{H^+ A^-}{HA})\] Splitting the log terms; \[Log Ka = log H^+ + log (\frac{A^-}{HA})\] Since pKa = -log10 Ka and pH = -log10 [H+], therefore: -pKa = – pH + \[ log (\frac{A^-}{HA}) \] pH = pKa + \[ log (\frac{A^-}{HA})\] This equation can also be written as: pH = pKa + \[log \frac{(salt)}{(acid)}\] 4. Weak Acid and Weak Base Here since both, acid and base, is weak neither of them dissociates completely and so neutralization does not occur. Equilibrium is the state when the rate of formation of product is equal to the rate of formation of the reactants.
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