When an acid and a base are mixed, they cancel each other’s properties. This reaction is called neutralization, and the substance produced is called a salt.
Basic Knowledge
A neutralization reaction is a reaction in which H+ from an acid combines with OH- from a base to form water (H2O). At the same time, a substance formed when the anion of the acid combines with the cation of the base—a salt—is produced.
Representative neutralization reactions:HCl + NaOH → NaCl + H2O (sodium chloride and water)H2SO4 + 2NaOH → Na2SO4 + 2H2O (sodium sulfate and water)HCl + Ca(OH)2 → CaCl2 + H2O (calcium chloride and water)
A heat of neutralization is produced in a neutralization reaction. The point at which the neutralization reaction is complete is called the neutralization point.
Neutralization (a reaction in which an acid and an alkali react and H+ and OH- become water)
Salt (a substance produced in a neutralization reaction. NaCl, Na2SO4, and so on)
Neutralization point (the point at which an acid and a base have reacted completely without either being in excess)
Heat of neutralization (heat produced by a neutralization reaction. Neutralization of a strong acid and strong base is about 57 kJ/mol)
Titration (the process of gradually adding a base (or acid) of known concentration to an acid (or base) of unknown concentration to determine the neutralization point)
Calcium carbonate (the main component of limestone and shells. CaCO3. Produces CO2 when it reacts with an acid)
Further Study
Neutralization also appears widely in daily life.
・Antacids that neutralize stomach acid (hydrochloric acid) contain sodium hydrogen carbonate (baking soda, NaHCO3) or aluminum hydroxide.
・In agriculture, slaked lime (Ca(OH)2) is added to acidic soil for neutralization.
・Lime (CaCO3) may also be spread in lakes and rivers to counteract acid rain.
Neutralization reaches the neutralization point when the amount of H+ equals the amount of OH- (acid valency × molar concentration × volume = base valency × molar concentration × volume).
- Neutralization = H+ + OH- → H2O (water is produced)
- A salt is produced at the same time
- Be able to write
HCl + NaOH → NaCl + H2Oreliably - Neutralization is an exothermic reaction (heat of neutralization is produced)
- An antacid is a base that neutralizes stomach acid (HCl)
- Slaked lime is used to improve soil (it neutralizes acidic soil)
- Neutralization point: amount of H+ = amount of OH-
Points to Note
① In chemistry, the word salt includes many substances besides NaCl. ② Neutralization does not necessarily produce a neutral solution (for example, a salt of a strong acid and a weak base may be acidic). ③ Distinguish the 1:1 coefficients in HCl + NaOH → NaCl + H2O from the 1:2 coefficients in H2SO4 + 2NaOH →.
Practice
- Write the chemical equation for the neutralization reaction between hydrochloric acid and sodium hydroxide solution.
- Using the terms “H+” and “OH-,” explain what kind of reaction neutralization is.
- From the viewpoint of neutralization, explain why an antacid in the stomach is basic.