Acid and Carbonate Word Equations Chemistry Tutorial

Key Concepts

In general an acid reacts with a carbonate or hydrogencarbonate to produce a salt, carbon dioxide gas and water.
Hydrogencarbonate is also referred to as hydrogen carbonate⁽¹⁾

The reaction between an acid and a carbonate can be represented by the general word equation shown below:
acid + carbonate → salt + carbon dioxide + water

The name of the salt is determined by the metal part of the carbonate, and, the acid used:

general word equation:	acid	+	metal carbonate	→	salt	+	carbon dioxide	+	water
hydrochloric acid example :	hydrochloric acid	+	metal carbonate	→	metal chloride	+	carbon dioxide	+	water
nitric acid example :	nitric acid	+	metal carbonate	→	metal nitrate	+	carbon dioxide	+	water
sulfuric acid⁽²⁾ example :	sulfuric acid	+	metal carbonate	→	metal sulfate	+	carbon dioxide	+	water
phosphoric acid example :	phosphoric acid	+	metal carbonate	→	metal phosphate	+	carbon dioxide	+	water

The reaction between an acid and a hydrogencarbonate can be represented by the general word equation shown below:
acid + hydrogencarbonate → salt + carbon dioxide + water

The name of the salt is determined by the metal part of the hydrogencarbonate, and, the acid used:

general word equation:	acid	+	metal hydrogencarbonate	→	salt	+	carbon dioxide	+	water
hydrochloric acid example :	hydrochloric acid	+	metal hydrogencarbonate	→	metal chloride	+	carbon dioxide	+	water
nitric acid example :	nitric acid	+	metal hydrogencarbonate	→	metal nitrate	+	carbon dioxide	+	water
sulfuric acid example :	sulfuric acid	+	metal hydrogencarbonate	→	metal sulfate	+	carbon dioxide	+	water
phosphoric acid example :	phosphoric acid	+	metal hydrogencarbonate	→	metal phosphate	+	carbon dioxide	+	water

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Determining the Products of the Chemical Reaction Between an Acid and a Carbonate (or Hydrogencarbonate)

Carbonates turn up in some surprising places; the shells of animals that live in the sea, bird's egg shells, animal teeth and bones, limestone, marble, cement, even toothpaste! Hydrogencarbonate is found in bicarbonate of soda (or sodium bicarbonate) which is used in baking to make cakes rise, and it is also found in antacid tablets and powders which you take if you are experiencing indigestion.⁽³⁾

If you place a piece of calcium carbonate (such as is found in limestone) in some hydrochloric acid in a test tube you will observe bubbles of gas being formed on the surface of the calcium carbonate (limestone).
These bubbles of gas tell us that a new substance is being formed and therefore a chemical reaction is taking place.

If we pass this gas through colourless limewater, the limewater will become milky-white. This tells us that the gas produced is carbon dioxide.

If we wait until all the carbonate has reacted and then boil off the liquid we find that at about 100°C the temperature doesn't change until all the liquid has boiled off.
The boiling point of water is about 100°C, so we can identify this liquid as water.⁽⁴⁾
When all the water has boiled off, we would be left with a white solid which is a salt.

You could repeat this chemical reaction using a different acid, sulfuric acid.
In this experiment you add sulfuric acid to a piece of calcium carbonate in a test tube.
Bubbles of gas are produced, which, if you pass this gas through colourless limewater, will turn the limewater milky-white indicating that the gas is carbon dioxide.
You could boil off all the liquid and find that it boils at the boiling point of water (about 100°C), and, when all the water has boiled off you would be left with another white solid, another salt.

From these two experiments we could generalise and say that calcium carbonate will react with an acid to produce a salt, carbon dioxide and water.
We can write a word equation to represent this chemical reaction:

reactants			→	products
calcium carbonate	+	acid	→	salt	+	carbon dioxide	+	water

What if you repeat these experiments using a different carbonate, sodium carbonate for example?
If we add hydrochloric acid to sodium carbonate bubbles of gas are produced which will turn colourless limewater milky, and the liquid can be boiled off at about 100°C leaving a white salt.
If we add sulfuric acid to sodium carbonate bubbles of gas are produced which will turn colourless limewater milky, and the liquid can be boiled off at about 100°C leaving a white salt.

From these two experiments we could generalise and say that sodium carbonate will react with an acid to produce a salt, carbon dioxide and water.
We can write a word equation to represent this chemical reaction:

reactants			→	products
sodium carbonate	+	acid	→	salt	+	carbon dioxide	+	water

From all of the above experiments, we could make an even more general statement about the products of a chemical reaction between an acid and a metal carbonate (a cabonate):

A metal carbonate reacts with an acid to produce a salt, carbon dioxide and water.

and we could write a general word equation to describe this generalisation:

reactants			→	products
metal carbonate	+	acid	→	salt	+	carbon dioxide	+	water
carbonate	+	acid	→	salt	+	carbon dioxide	+	water

You could repeat all of the experiments above using a metal hydrogencarbonate such as sodium hydrogencarbonate.
When you add an acid to this metal hydrogen carbonate a gas is produced that can turn colourless limewater milky, and you can boil off the liquid at about 100°C leaving a white solid behind which is a salt.
We can write a general word equation for the reaction between an acid and a metal hydrogencarbonate as shown below:

reactants			→	products
metal hydrogencarbonate	+	acid	→	salt	+	carbon dioxide	+	water
hydrogencarbonate	+	acid	→	salt	+	carbon dioxide	+	water

If you add an acid to a metal carbonate you produce a salt, carbon dioxide and water.
If you add an acid to a metal hydrogencarbonate you also produce a salt, carbon dioxide and water.

But what is the "salt" made up of? ⁽⁵⁾

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Naming the Salt Produced in the Reaction Between an Acid and a Metal Carbonate (or metal hydrogencarbonate)

The salt produced when a carbonate (or hydrogencarbonate) reacts with an acid will be made up of 2 parts:

a metal (the metal from the metal carbonate or hydrogencarbonate used in the experiment)

a non-metal (from the acid used in the experiment)

The name of the salt is written as two words:⁽⁶⁾

first word is the name of the metal (from the metal carbonate or hydrogencarbonate)

second word depends on the acid used:
(i) chloride (if hydrochloric acid is used)

(ii) nitrate (if nitric acid is used)

(iii) sulfate (if sulfuric acid is used)

(iv) phosphate (if phosphoric acid is used)

So, in general, the name of the salt produced when a metal carbonate (or metal hydrogencarbonate) reacts with an acid will be either:

metal chloride (if hydrochloric acid is used)

metal nitrate (if nitric acid is used)

metal sulfate (if sulfuric acid is used)

metal phosphate (if phosphoric acid is used)

Therefore, we can write some general word equations to describe the chemical reaction between a metal carbonate and an acid that produces a salt, carbon dioxide and water:

	reactants			→	products
general word equation:	metal carbonate	+	acid	→	salt	+	carbon dioxide	+	water
Example :	metal carbonate	+	hydrochloric acid	→	metal chloride	+	carbon dioxide	+	water
Example :	metal carbonate	+	nitric acid	→	metal nitrate	+	carbon dioxide	+	water
Example :	metal carbonate	+	sulfuric acid	→	metal sulfate	+	carbon dioxide	+	water
Example :	metal carbonate	+	phosphoric acid	→	metal phosphate	+	carbon dioxide	+	water

Similarly, we can write some general word equations to describe the chemical reaction between a metal hydrogencarbonate and an acid that produces a salt, carbon dioxide and water:

	reactants			→	products
general word equation:	metal hydrogencarbonate	+	acid	→	salt	+	carbon dioxide	+	water
Example :	metal hydrogencarbonate	+	hydrochloric acid	→	metal chloride	+	carbon dioxide	+	water
Example :	metal hydrogencarbonate	+	nitric acid	→	metal nitrate	+	carbon dioxide	+	water
Example :	metal hydrogencarbonate	+	sulfuric acid	→	metal sulfate	+	carbon dioxide	+	water
Example :	metal hydrogencarbonate	+	phosphoric acid	→	metal phosphate	+	carbon dioxide	+	water

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De-coding a Word Equation for the Reaction Between an Acid and a Carbonate (or hydrogencarbonate)

Recall the following facts:

In a word equation the reactants are written on the left hand side of the arrow and each reactant is separated by a plus sign (+)

In a word equation the products are written on the right hand side of the arrow and each product is separated by a plus sign (+)

The name of the carbonate (or hydrogencarbonate) will be two words: metal carbonate (or metal hydrogencarbonate)

The name of the acid will be two words, the second word will be acid.

The name of the salt will be two words, the name of the metal is the first word, the second word comes from the name of the acid used.

Carbon dioxide and water will also be products when a metal carbonate (or metal hydrogencarbonate) reacts with an acid.

For the chemical reaction between an acid and a metal carbonate, the products are a salt, carbon dioxide and water.
metal carbonate + acid → salt + carbon dioxide + water

For the chemical reaction between an acid and a metal hydrogencarbonate, the products are a salt, carbon dioxide and water.
metal hydrogencarbonate + acid → salt + carbon dioxide + water

If we are given the following word equation:

magnesium carbonate + hydrochloric acid → magnesium chloride + carbon dioxide + water

then we can identify the reactants and products of the chemical reaction:

reactants	→	products
magnesium carbonate + hydrochloric acid	→	magnesium chloride + carbon dioxide + water

The reactants are:

magnesium carbonate

hydrochloric acid

The products are:

magnesium chloride ⁽⁷⁾

carbon dioxide

water

We can also identify the carbonate and acid reactants, and the salt, gas and water produced:

reactants			→	products
carbonate	+	acid	→	salt	+	carbon dioxide gas	+	water
magnesium carbonate	+	hydrochloric acid	→	magnesium chloride	+	carbon dioxide	+	water

carbonate is magnesium carbonate

acid is hydrochloric acid

salt is magnesium chloride

gas is carbon dioxide

liquid is water

And we can infer what the experimenter may have done: some hydrochloric acid was added to some magnesium carbonate.

And we can infer what the experimenter may have observed if the gas was passed through colourless limewater: the limewater turned milky-white.

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Problem Solving

The Problem: Jo the Geologist gave Chris the Chemist a white mineral which was believed to be potassium carbonate. Chris added sulfuric acid to a sample of the mineral, collected the gas given off and passed it through a colourless solution of limewater which turned milky. Chris boiled off all the liquid at 99.8°C, the boiling point of water in the laboratory. Then Chris placed some of the white salt remaining in a flame and it produced a lovely lilac colour indicating the presence of potassium. Write a word equation to describe the reaction between the mineral containing potassium carbonate and sulfuric acid.

The Solution to the Problem

(using the StoPGoPS approach to problem solving)

STOP

STOP! State the Question.

What is the question asking you to do?

Write a word equation for the chemical reaction between potassium carbonate and sulfuric aicd.

PAUSE

PAUSE to Prepare a Game Plan

(1) What information (data) have you been given in the question?

(a) Name of the reactants: potassium carbonate and sulfuric acid

(b) Evidence of a chemical reaction: gas produced

(i) salt containing potassium (flame colour)

(ii) carbon dioxide (gas turned limewater milky)

(iii) water (boiling point of liquid)

(2) What is the relationship between what you know and what you need to find out?

General word equation: acid + metal carbonate → salt + carbon dioxide + water

The name of the salt will be 2 words: the first word is the name of the metal from the metal carbonate, the second word comes from the name of the acid:

hydrochloric acid → metal chloride

nitric acid → metal nitrate

sulfuric acid → metal sulfate

phosphoric acid → metal phosphate

GO with the Game Plan

General word equation:	carbonate	+	acid	→	salt	+	carbon dioxide	+	water
General word equation:	reactants			→	products
General word equation:	metal carbonate	+	sulfuric acid	→	metal sulfate	+	carbon dioxide	+	water
Substitute the name of each reactant and each product into the general word equation:
word equation:	potassium carbonate	+	sulfuric acid	→	potassium sulfate	+	carbon dioxide	+	water

PAUSE

PAUSE to Ponder Plausibility

Have you answered the question?

Yes, we have written a word equation for the reaction between potassium carbonate and sulfuric acid.

Is your answer plausible?

De-code the word equation you wrote to try to re-create Chris's experiment.

The reactants are potassium carbonate and sulfuric acid, so Chris added sulfuric acid to potassium carbonate.

When a carbonate reacts with an acid carbon dioxide is produced (the gas that turns limewater milky) and water which boils at about 100°C is also produced.
The salt produced, potassium sulfate, would be a white solid that produces a lilac flame in a flame test.

Since we can de-code our word equation to arrive at what Chris actually did and what was observed, we are confident our word equation is correct.

STOP

STOP! State the Solution

potassium carbonate + sulfuric acid → potassium sulfate + carbon dioxide + water

Footnotes:

(1) If you are an inorganic Chemist, you will refer to this as hydrogencarbonate (just one word), but you will also see the substance referred to as hydrogen carbonate (two words) which is most commonly used by organic Chemists.
The IUPAC systematic additive name for this compound is hydroxidodioxidocarbonate(1-).
The acceptable IUPAC "hydrogen name" for the same species is hydrogen(trioxidocarbonate)(1-)
Refer to "Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005" (Red Book) for more about naming inorganic compounds.
If you come across an even older textbook you will find hydrogencarbonates referred to as bicarbonates. The term bicarbonate is still in general useage (you probably have a box of sodium bicarbonate in your kitchen pantry!) but you should avoid using this in Chemistry. Use hydrogencarbonate instead.

(2) In older textbooks you will see sulfuric acid written as sulphuric acid ("ph" instead of "f").
IUPAC gives the name of the element sulfur with an "f" not a "ph" so the acid is sulfuric acid.
The name of a salt derived from sulfuric aicd (with an "f") is a sulfate (also with an "f"), but in older textbooks you will find that the salts derived from sulphuric acid (with a "ph") are called sulphates (also with a "ph").

(3) For more fascinating uses for sodium hydrogencarbonate (sodium bicarbonate), see the March 2018 isuue of AUS-e-NEWS.

(4) The temperature that water boils at will depend on where you are.
If you happen to be in place where atmospheric pressure is 1 atmosphere, then water will boil at 100°C.
If you are above sea-level, up a hill or a mountain, then the boiling point of water will less than 100°C
If you reduce the air pressure enough, such as in a evacuated bell jar, you can boil water at room temperature!

(5) We could perform some tests on the salt to determine what it is made up of:

(i) Flame Test: identifies the metal by the colour of its flame.

(ii) Solubility Tests: identifies the anion by precipitation of an insoluble solid:

(a) Add barium nitrate: if a precipitate forms the salt solution contain sulfate.

(b) If no precipitate forms in (a) then add silver nitrate solution, if a precipitate forms the salt solution contains chloride.

(6) If you name the hydrogencarbonate (1 word) as hydrogen carbonate (2 words), then the name of the salt will be 3 words: metal hydrogen carbonate, instead of 2 words: metal hydrogencarbonate.

(7) Some metals, like iron, can form ions with different positive charges. Iron can form ions with a charge of 1+, 2+ or 3+.
The name of the cations of iron are therefore: iron(1+), iron(2+), and iron(3+).
The name of the salt formed by these cations must include the name of the metal AND its charge: iron(1+) chloride, iron(2+) chloride, iron(3+) chloride.
Iron can also form covalent compounds. In this case there is no cation, no positive charge, but we can assign an informal charge based on its oxidation state (which is then referred to as its oxidation state or oxidation number). When we do this, we use Roman numerals to indicate the oxidation state of the metal. For iron the oxidation states are iron(I), iron(II), and iron(III).
The Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005 ("Red Book") for the naming of salts (binary inorganic ionic compounds) recommends the use of the charge number (1+, 2+, 3+) instead of the oxidation state (I, II, III).