To Determine the Enthalpy of Neutralization of a Strong Acid(HCl) with a Sturdy Base (NaOH)

Our Objective 

To determine the enthalpy of neutralization of a strong acid (HCl) with a sturdy base (NaOH). 


The Theory 

H+ (aq) ions from an acid and OH- (aq) ions from a base are combined in a neutralization process, which obviously results in the creation of H2O. (l). This reaction is usually exothermic since it involves the creation of bonds. The amount of heat released when 1 mole of H+ ions provided by the acid and 1 mole of OH- ions provided by the base unite to produce water is known as the enthalpy of neutralization Thus:  

                          H+ (aq) + OH– (aq) → H2O (l),  ∆neut H is negative 

                          (Acid)          (Base) 

where the term " neut H" refers to the enthalpy of neutralization. If the acid and the base are both potent, then 57 kJ mol-1 of heat is always released in order produce 1 mol of H2O (l). If either the acid or the base is weak, or if both are weak, some of the heat released is utilized to ionize the weaker of the two, depending on the situation, and the quantity of heat released is less than 57 kJ mol-1. 

Neutralization Enthalpy of Strong Base and Strong Acid 

The neutralization enthalpy is constant for strong bases and acids. This is because a diluted solution fully ionizes both strong acids and strong bases. When an acid and an alkali combine, heat is generated, which causes neutralization changes in enthalpy to frequently be negative. 

Neutralization Reaction 

A neutralization process has to combine H+ ions and OH- ions to make water, much as an acid and a base reaction does to create water and salt. The neutralization of a strong acid and heavy acid has a pH requirement of 7. The resultant pH will be larger than 7 when a strong base neutralizes a weak acid. In contrast, neutralizing a strong acid and a weak base would have pH of less than 7 

STEP 1: Determine the heat that has evolved: Total mass of the reaction mixture is given by  q = m Cg T m 

M  = total mass of reaction mixture 

Cg = the solution's particular heat capacity. 

T   = change of solution's temperature 

STEP 2: Determine the reaction's change in enthalpy: ΔH = −q 

STEP 3: The molar enthalpy of neutralization should be calculated. 

                       ΔneutH =   ΔH ÷ n(H2O(l) 

Enthalpy of Neutralization: Strong Monoprotic Acid + Strong Monobasic Base 

Strong monoprotic acid HCl(aq), which produces hydrogen ions (H+(aq)) and chloride ions (Cl-(aq)) when it completely dissociates (ionizes) in water: 

                                              HCl(aq) → H+(aq) + Cl-(aq) 

                           n(HCl(aq)): n(H+(aq)) is 1:1 (that is, monoprotic) 

Sodium ions (Na+(aq)) and hydroxide ions (OH-(aq)) are produced by the strong monobasic base NaOH(aq), which totally dissociates (ionizes) in water. 

                                               NaOH(aq) → Na+(aq) + OH-(aq) 

                          n(NaOH(aq)): n(OH-(aq)) is 1:1 (that is, monobasic) 

A neutralization reaction occurs when HCl(aq) is added to NaOH(aq) 

                                              HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq) 

and heat energy is given off (the reaction is exothermic) 


Learning Outcomes 

  • The distinction between strong and weak electrolytes can be made clear to students. 
  • Students are aware of the neutralization enthalpy. 
  • They can understand the chemistry behind this reaction