Identify usual acids and basesDefine acid-base reactionsRecognize and also identify examples of acid-base reactionsPredict the products of acid-base reactions.

You are watching: Write the molecular equation for the acid-base reaction represented here. include phases.

The meaning of an acid is often cited as: any compound that boosts the amount of hydrogen ion (H+) in one aqueous solution. The chemical opposite the an acid is a base. The equivalent meaning of a base is that a base is a link that rises the lot of hydroxide ion (OH−) in one aqueous solution. These original meanings were proposed by Arrhenius (the same human being who proposed ion dissociation) in 1884, for this reason they are described as the Arrhenius definition of one acid and also a base, respectively.

You may recognize that, based on the description of a hydrogen atom, an H+ ion is a hydrogen atom that has lost its lone electron; the is, H+ is merely a proton. Carry out we really have bare proton moving around in aqueous solution? No. What is more likely is that the H+ ion has attached itself to one (or more) water molecule(s). To represent this chemically, we specify the hydronium ion H3O+(aq), a water molecule with an extra hydrogen ion attached come it. As H3O+, i m sorry represents an additional proton attached come a water molecule. We usage the hydronium ion together the more logical method a hydrogen ion appears in one aqueous solution, return in numerous chemical reactions H+ and H3O+ are treated equivalently.

For purposes of this quick introduction, we will think about only the much more common types of acid-base reactions the take location in aqueous solutions. In this context, one acid is a problem that will dissolve in water to yield hydronium ions, H3O+. As an example, take into consideration the equation displayed here:

extHCl(aq) + extH_2 extO(aq) longrightarrow extCl^-(aq) + extH_3 extO^+(aq)

The procedure represented by this equation confirms the hydrogen chloride is one acid. When dissolved in water, H3O+ ion are created by a chemistry reaction in i beg your pardon H+ ions space transferred indigenous HCl molecule to H2O molecule (Figure 1).

Figure 1. as soon as hydrogen chloride gas disappear in water, (a) the reacts as an acid, carrying protons to water molecule to yield (b) hydronium ion (and solvated chloride ions).

The nature of HCl is such the its reaction through water together just explained is essentially 100% efficient: virtually every HCl molecule that dissolves in water will certainly undergo this reaction. Mountain that completely react in this fashion are called strong acids, and HCl is one among just a grasp of usual acid compound that are classified as strong (Table 1).

Compound FormulaName in Aqueous Solution
HBrhydrobromic acid
HClhydrochloric acid
HIhydroiodic acid
HNO3nitric acid
HClO4perchloric acid
HClO3chloric acid
H2SO4sulfuric acid
Table 1. Common strong Acids

 A much greater variety of compounds behave as weak acids and also only partly react through water, leaving a large majority of liquified molecules in their original form and generating a fairly small quantity of hydronium ions.

Compound FormulaName in Aqueous Solution
HFhydrofluoric acid
HCNhydrocyanic acid
HC2H3O2acetic acid
HNO2nitrous acid
HClOhypochlorous acid
HClO2chlorous acid
H2SO3sulfurous acid
H2CO3carbonic acid
H3PO4phosphoric acid
Table 2. typical Weak Acids

Weak acids are typically encountered in nature, being the substances partly responsible because that the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells connected with body odor. A familiar example of a weak acid is acetic acid, the main ingredient in food vinegars:

extCH_3 extCO_2 extH(aq) + extH_2 extO(l) leftrightharpoons extCH_3 extCO_2^-(aq) + extH_3 extO^+(aq)
Figure 2. (a) fruits such as oranges, lemons, and also grapefruit save on computer the weak acid citric acid. (b) Vinegars save the weak acid acetic acid. (credit a: alteration of work by Scott Bauer; credit b: change of work by Brücke-Osteuropa/Wikimedia Commons)

A base is a problem that will certainly dissolve in water to productivity hydroxide ions, OH−. The most typical bases are ionic compounds created of alkali or alkaline planet metal cations (groups 1 and also 2) linked with the hydroxide ion—for example, NaOH and Ca(OH)2. As soon as these compounds dissolve in water, hydroxide ions room released straight into the solution. For example, KOH and Ba(OH)2 dissolve in water and also dissociate fully to develop cations (K+ and Ba2+, respectively) and also hydroxide ions, OH−. This bases, together with other hydroxides that completely dissociate in water, are considered strong bases.

Consider as an example the dissolution of lye (sodium hydroxide) in water:

extNaOH(s) longrightarrow extNa^+(aq) + extOH^-(aq)

This equation confirms that salt hydroxide is a base. When dissolved in water, NaOH dissociates to productivity Na+ and also OH− ions. This is also true for any type of other ionic link containing hydroxide ions. Since the dissociation procedure is essentially complete when ionic compounds dissolve in water under common conditions, NaOH and also other ionic hydroxides room all classified as strong bases.

Unlike ionic hydroxides, some compounds produce hydroxide ions when liquified by chemically reacting with water molecules. In every cases, these compounds react only partially and also so space classified together weak bases. These types of compound are additionally abundant in nature and also important commodities in miscellaneous technologies. For example, global production that the weak basic ammonia is generally well over 100 metric loads annually, being widely offered as an farming fertilizer, a raw material for chemistry synthesis of other compounds, and an active ingredient in family cleaners (Figure 3). When dissolved in water, ammonia reacts partially to productivity hydroxide ions, as presented here:

extNH_3(aq) + extH_2 extO(l) ightleftharpoons extNH_4^+(aq) + extOH^-(aq)

Under common conditions, only about 1% that the dissolved ammonia is present as NH4+ ions.

Figure 3. Ammonia is a weak base offered in a selection of applications. (a) Pure ammonia is commonly applied as an agricultural fertilizer. (b) Dilute remedies of ammonia are efficient household cleansers. (credit a: change of occupational by national Resources conservation Service; credit transaction b: alteration of work-related by pat00139)

Acid-Base Reactions

An acid-base reaction is one in i beg your pardon a hydrogen ion, H+, is moved from one chemical types to another. Such reactions room of main importance to plenty of natural and technological processes, varying from the chemical revolutions that take location within cells and also the lakes and also oceans, to the industrial-scale manufacturing of fertilizers, pharmaceuticals, and also other substances necessary to society. The subject of acid-base chemistry, therefore, is worthy of thorough discussion.

The reaction in between an acid and also a base is called an acid-base reaction or a neutralization reaction. Return acids and also bases have their own distinct chemistries, the acid and also base cancel every other’s chemistry to develop a quite innocuous substance—water. In fact, the general acid-base reaction is

acid + base longrightarrow water + salt

where the hatchet salt is used to define any kind of ionic compound (soluble or insoluble) the is developed from a reaction between an acid and also a base. In chemistry, the word salt advert to an ext than simply table salt. Because that example, the well balanced chemical equation because that the reaction between HCl(aq) and KOH(aq) is

HCl(aq) + KOH(aq) longrightarrow H2O(ℓ) + KCl(aq)

where the salt is KCl. By count the variety of atoms of each element, we discover that only one water molecule is developed as a product. However, in the reaction between HCl(aq) and Mg(OH)2(aq), added molecules the HCl and also H2O are required to balance the chemistry equation:

2 HCl(aq) + Mg(OH)2(aq) longrightarrow 2 H2O(ℓ) + MgCl2(aq)

Here, the salt is MgCl2. This is among several reactions that take place when a form of antacid—a base—is provided to act stomach acid.

There room acid-base reactions that do not follow the “general acid-base” equation provided above. Because that example, , the well balanced chemical equation for the reaction in between HCl(aq) and also NH3(aq) is

HCl(aq) + NH3(aq) longrightarrow NH4Cl(aq)

Example 1

Write the neutralization reactions between each acid and also base.

a) HNO3(aq) and also Ba(OH)2(aq) b)H3PO4(aq) and also Ca(OH)2(aq)


First, we will write the chemistry equation with the recipe of the reactants and the intended products; climate we will certainly balance the equation.

a) The expected commodities are water and barium nitrate, therefore the initial chemistry reaction is

HNO3(aq) + Ba(OH)2(aq) longrightarrow H2O(ℓ) + Ba(NO3)2(aq)

To balance the equation, we must realize the there will certainly be two H2O molecules, so two HNO3 molecules are required:

2HNO3(aq) + Ba(OH)2(aq) longrightarrow 2H2O(ℓ) + Ba(NO3)2(aq)

This chemical equation is currently balanced.

b) The expected products are water and calcium phosphate, so the initial chemistry equation is

H3PO4(aq) + Ca(OH)2(aq) longrightarrow H2O(ℓ) + Ca3(PO4)2(s)

According come the solubility rules, Ca3(PO4)2 is insoluble, therefore it has actually an (s) phase label. To balance this equation, we need two phosphate ions and three calcium ions; we finish up with 6 water molecule to balance the equation:

2 H3PO4(aq) + 3 Ca(OH)2(aq) longrightarrow 6 H2O(ℓ) + Ca3(PO4)2(s)

This chemistry equation is currently balanced.

Test Yourself

Write the neutralization reaction in between H2SO4(aq) and also Sr(OH)2(aq).


H2SO4(aq) + Sr(OH)2(aq) longrightarrow 2 H2O(ℓ) + SrSO4(aq)

Neutralization reactions are one type of chemistry reaction that proceeds even if one reactant is not in the aqueous phase. Because that example, the chemistry reaction in between HCl(aq) and Fe(OH)3(s) tho proceeds follow to the equation

3 HCl(aq) + Fe(OH)3(s) longrightarrow 3 H2O(ℓ) + FeCl3(aq)

even despite Fe(OH)3 is no soluble. As soon as one realizes that Fe(OH)3(s) is a component of rust, this explains why some cleaning remedies for rust stains save acids—the neutralization reaction produces products that room soluble and wash away. Washing v acids prefer HCl is one means to remove rust and rust stains, but HCl should be used with caution!

Complete and net ionic reactions because that neutralization reaction will count on whether the reactants and products space soluble, also if the acid and base react. For example, in the reaction that HCl(aq) and NaOH(aq),

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

the complete ionic reaction is

H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) longrightarrow H2O(ℓ) + Na+(aq) + Cl−(aq)

The Na+(aq) and Cl−(aq) ions are spectator ions, therefore we deserve to remove them to have

H+(aq) + OH−(aq) longrightarrow H2O(ℓ)

as the net ionic equation. If we want to compose this in regards to the hydronium ion, H3O+(aq), we would write it as

H3O+(aq) + OH−(aq) longrightarrow 2H2O(ℓ)

With the exception of the development of an extra water molecule, these two net ionic equations space equivalent.

However, for the reaction in between HCl(aq) and also Cr(OH)2(s), due to the fact that chromium(II) hydroxide is insoluble, us cannot different it into ions for the finish ionic equation:

2 H+(aq) + 2 Cl−(aq) + Cr(OH)2(s) longrightarrow 2 H2O(ℓ) + Cr2+(aq) + 2 Cl−(aq)

The chloride ions space the only spectator ions here, therefore the net ionic equation is

2 H+(aq) + Cr(OH)2(s) longrightarrow 2 H2O(ℓ) + Cr2+(aq)

Example 2

Write well balanced chemical equations because that the acid-base reactions explained here:

a) the weak acid hydrogen hypochlorite reacts with water

b) a systems of barium hydroxide is neutralized v a equipment of nitric acid

Solutiona) The two reactants are provided, HOCl and also H2O. Since the problem is report to be an acid, that reaction v water will involve the carry of H+ indigenous HOCl to H2O to create hydronium ions, H3O+ and also hypochlorite ions, OCl−.

extHOCl(aq) + extH_2 extO(l) ightleftharpoons extOCl^-(aq) + extH_3 extO^+(aq)

A double-arrow is ideal in this equation since it shows the HOCl is a weak acid that has not reacted completely.

b) The two reactants space provided, Ba(OH)2 and also HNO3. Due to the fact that this is a neutralization reaction, the two products will it is in water and also a salt composed of the cation that the ionic hydroxide (Ba2+) and also the anion produced when the mountain transfers its hydrogen ion (NO3−).

extBa(OH)_2(aq) + 2 extHNO_3(aq) longrightarrow extBa(NO_3)_2(aq) + 2 extH_2 extO(l)

Test YourselfWrite the net ionic equation representing the neutralization of any solid acid with an ionic hydroxide. Hint: think about the ions created when a strong acid is liquified in water.


extH_3 extO^+(aq) + extOH^-(aq) longrightarrow 2 extH_2 extO(l)

Example 3

Oxalic acid, H2C2O4(s), and also Ca(OH)2(s) react really slowly. What is the network ionic equation between these 2 substances if the salt developed is insoluble? The anion in oxalic mountain is the oxalate ion, C2O42−.


The commodities of the neutralization reaction will certainly be water and calcium oxalate:

H2C2O4(s) + Ca(OH)2(s) longrightarrow 2 H2O(ℓ) + CaC2O4(s)

Because nothing is dissolved, there are no substances come separate into ions, for this reason the network ionic equation is the equation of the three solids and one liquid.

Test Yourself

What is the network ionic equation in between HNO3(aq) and Ti(OH)4(s)?


4 H+(aq) + Ti(OH)4(s) longrightarrow 4 H2O(ℓ) + Ti4+(aq)


Explore the microscopic see of strong and weak acids and bases.

Gas-forming Acid-Base reactions

A driving pressure for particular acid-base reactions is the development of a gas. Typical gases formed are H2, O2, and CO2.

For example:

2HCl(aq) + Na2CO3(aq) longrightarrow H2CO3(aq) + 2NaCl(aq) longrightarrow CO2(g) + H2O(l) + 2NaCl(aq)

The above example can be perceived as one acid-base reaction adhered to by a decomposition. The driving pressure in this instance is the gas formation. The decomposition the H2CO3 into CO2 and H2O is a very common reaction. Both Na2CO3 and also NaHCO3 combined with acid result in a gas-forming acid-base reaction.

HCl(aq) + NaHCO3(aq) longrightarrow H2CO3(aq) + NaCl(aq) longrightarrow CO2(g) + H2O(l) + NaCl(aq)

Food and also Drink App: acids in Foods

Many foods and also beverages save acids. Acids impart a sour keep in mind to the taste that foods, which may add some pleasantness come the food. Because that example, orange juice contains citric acid, H3C6H5O7. Note how this formula mirrors hydrogen atom in two places; the first hydrogen atoms written are the hydrogen atoms the can type H+ ions, if the 2nd hydrogen atoms created are part of the citrate ion, C6H5O73−. Lemons and also limes save on computer much more citric acid—about 60 times together much—which accounts because that these citrus fruit being much more sour than many oranges. Vinegar is essentially a ~5% systems of acetic mountain (HC2H3O2) in water. Apples contain malic acid (H2C4H4O5; the name malic acid comes from the apple’s botanical genus name, malus), if lactic mountain (HC3H5O3) is found in wine and also sour milk products, such together yogurt and also some cottage cheeses.

Table 3 “Various Acids discovered in Food and Beverages” lists some acids discovered in foods, either normally or together an additive. Frequently, the salts of acid anions are used as additives, such together monosodium glutamate (MSG), i m sorry is the sodium salt acquired from glutamic acid. Together you review the list, girlfriend should involved the unavoidable conclusion that it is difficult to protect against acids in food and also beverages.

Acid NameAcid FormulaUse and also Appearance
acetic acidHC2H3O2flavouring; uncovered in vinegar
adipic acidH2C6H8O4flavouring; discovered in processed foods and also some antacids
alginic acidvariousthickener; uncovered in drinks, ice cream, and weight ns products
ascorbic acidHC6H7O6antioxidant, also known together vitamin C; discovered in fruits and vegetables
benzoic acidHC6H5CO2preservative; found in handle foods
citric acidH3C6H5O7flavouring; found in citrus fruits
dehydroacetic acidHC8H7O4preservative, specifically for strawberries and also squash
erythrobic acidHC6H7O6antioxidant; found in processed foods
fatty acidsvariousthickener and also emulsifier; uncovered in handle foods
fumaric acidH2C4H2O4flavouring; mountain reactant in some baking powders
glutamic acidH2C5H7NO4flavouring; found in processed foods and also in tomatoes, some cheeses, and soy products
lactic acidHC3H5O3flavouring; discovered in wine, yogurt, cottage cheese, and also other cake milk products
malic acidH2C4H4O5flavouring; discovered in apples and also unripe fruit
phosphoric acidH3PO4flavouring; discovered in part colas
propionic acidHC3H5O2preservative; uncovered in baked goods
sorbic acidHC6H7O2preservative; uncovered in processed foods
stearic acidHC18H35O2anticaking agent; found in hard candies
succinic acidH2C4H4O4flavouring; discovered in wine and beer
tartaric acidH2C4H4O6flavouring; found in grapes, bananas, and also tamarinds

Table 3. Various Acids found in Food and also Beverages

Key Concepts and also Summary

Chemical reactions room classified according to similar patterns of behaviour. Acid-base reaction involve the transfer of hydrogen ions in between reactants.

General acid-base reactions, additionally called neutralization reactions deserve to be summarized v the adhering to reaction equation:

ACID(aq) + BASE(aq) longrightarrow H2O(l) + SALT(aq) or (s)

The DRIVING pressure for a basic acid-base reaction is the development of water.

Gas-forming acid-base reactions have the right to be summarized v the adhering to reaction equation:

ACID(aq) + NaHCO3 or Na2CO3(aq) longrightarrow H2O(l) + CO2(g) + SALT(aq) or (s)

The DRIVING force for a gas-forming acid-base reaction is the development of gas. There space three means of

There are three means of representing a neutralization reaction, utilizing a molecule equation, finish ionic equation or net ionic equation, as explained in section 6.1.

1. What is the Arrhenius definition of an acid?

2. What is the Arrhenius meaning of a base?

3. Suspect the products of each acid-base combination listed. Assume that a neutralization reaction occurs.

5. Create a balanced chemical equation for the neutralization reaction in between each given acid and also base. Include the suitable phase labels.

a) HI(aq) + KOH(aq) longrightarrow ?

b) H2SO4(aq) + Ba(OH)2(aq) longrightarrow ?

7. Write the complete and net ionic equations because that the neutralization reaction between HClO3(aq) and also Zn(OH)2(s). I think the salt is soluble.

8. Describe why the net ionic equation because that the neutralization reaction between HCl(aq) and also KOH(aq) is the exact same as the net ionic equation because that the neutralization reaction in between HNO3(aq) and RbOH.

9. Write the complete and net ionic equations because that the neutralization reaction between HCl(aq) and KOH(aq) utilizing the hydronium ion in ar of H+. What distinction does it make as soon as using the hydronium ion?

10. Complete and also balance the complying with acid-base equations:

a) HCl gas reacts through solid Ca(OH)2(s).

b) A systems of Sr(OH)2 is included to a systems of HNO3.

11. Complete and also balance the equations for the adhering to acid-base neutralization reactions. If water is offered as a solvent, compose the reactants and also products as aqueous ions. In some cases, there might be an ext than one correct answer, depending upon the amounts of reaction used.

a) extMg(OH)_2(s) + extHClO_4(aq) longrightarrow

b) extSrO(s) + extH_2 extSO_4(l) longrightarrow

12. Complete and also balance the equations that the complying with reactions, each of which could be provided to eliminate hydrogen sulfide from natural gas:

a) extCa(OH)_2(s) + extH_2 extS(g) longrightarrow

b) extNa_2 extCO_3(aq) + extH_2 extS(g) longrightarrow

4. a) HCl + KOH longrightarrow KCl + H2O

b) H2SO4 + 2 KOH longrightarrow K2SO4 + 2 H2O

c) 2 H3PO4 + 3 Ni(OH)2 longrightarrow Ni3(PO4)2 + 6 H2O

5. a) HI(aq) + KOH(aq) longrightarrow KCl(aq) + H2O(ℓ)

b) 2 H+(aq) + SO42−(aq) + Ba2+(aq) + 2 OH−(aq) longrightarrow BaSO4(s) + 2 H2O(ℓ)

7. Complete ionic equation:

2 H+(aq) + 2 ClO3−(aq) + Zn2+(aq) + 2 OH−(aq) longrightarrow Zn2+(aq) + 2 ClO3−(aq) + 2 H2O(ℓ)

8. Due to the fact that the salts room soluble in both cases, the net ionic reaction is simply H+(aq) + OH−(aq) longrightarrow H2O(ℓ).

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9. Complete ionic equation:

H3O+(aq) + Cl−(aq) + K+(aq) + OH−(aq) longrightarrow 2 H2O(ℓ) + K+(aq) + Cl−(aq)

Net ionic equation:

H3O+(aq) + OH−(aq) longrightarrow 2 H2O(ℓ)

The distinction is just the existence of one extra water molecule as a product.

10. a) 2 extHCl(g) + extCa(OH)_2(s) longrightarrow extCaCl_2(s) + 2 extH_2 extO(l);

b) extSr(OH)_2(aq) + 2 extHNO_3(aq) longrightarrow extSr(NO_3)_2(aq) + 2 extH_2 extO(l);

11. a) extMg(OH)_2(s) + 2 extHClO_4(aq) longrightarrow extMg^2+(aq) + 2 extClO_4^-(aq) + 2 extH_2 extO(l);b) extSrO(s) + extH_2 extSO_4(l) longrightarrow extSrSO_4(s) + extH_2 extO

12. a) extCa(OH)_2(s) + extH_2 extS(g) longrightarrow extCaS(s) + 2 extH_2 extO(l);b) extNa_2 extCO_3(aq) + extH_2 extS(g) longrightarrow extNa_2 extS(aq) + extCO_2(g) + extH_2 extO(l)


acid: substance that produces H3O+ when dissolved in water

acid-base reaction: reaction entailing the move of a hydrogen ion in between reactant species

base: substance the produces OH− when liquified in water

neutralization reaction: reaction in between an acid and also a base to create salt and water

salt: ionic link that can be formed by the reaction of an acid with a base that contains a cation and also an anion various other than hydroxide or oxide

strong acid: acid the reacts completely when liquified in water to productivity hydronium ions

strong base: base that reacts fully when dissolved in water to yield hydroxide ions

weak acid: acid that reacts just to a slight degree when dissolved in water to productivity hydronium ions

weak base: base the reacts only to a slight level when liquified in water to yield hydroxide ions