Laws of Chemical Combination in Chemistry | Types, eg

Definition of laws of Chemical Combination

Chemistry is the study of the transformation of matter from one form to the other. These transformations often occur as a result of the combination of two different types of matter. The combination of different elements to form compounds is governed by certain basic rules. These rules are referred to as laws of chemical combination.

laws of chemical combination
  • Chemical laws are those laws of nature relevant to chemistry

Basic Principle of laws of Chemical Combination

The laws of chemical combination describe the basic principles obeyed by interacting atoms and molecules, interactions that can include many different combinations that happen in many different ways.

This amazing diversity of interactions allows for an astounding variety of chemical reactions and compounds.

Spontaneous chemical reactions happen constantly, shaping the world around us, while humans engineer specific reactions to our benefit and attempt to curb reactions that hurt us.

Though chemical reactions can be as complex as they are numerous, they are all fundamentally governed by these same guiding laws of chemical combination, which lay the groundwork for the analysis of chemical reactions.

Types of laws of Chemical Combination

There are six basic laws of chemical combination that govern the chemical combinations of elements :

1. Law of Conservation of Mass

law of conservation of mass

In simple terms, this law states that matter can neither be created nor destroyed.

In other words, the total mass, that is, the sum of the mass of reacting mixture and the products formed remains constant.

Discovery

Antoine Lavoisier gave this law in the year 1789 based on the data he obtained after carefully studying numerous combustion reactions. We also refer to this law as the law of indestructibility of matter.

The mass and energy are interconvertible but the total sum of the mass and energy during any physical or chemical change remains constant.

Example

C + O2 -> CO2

C + O2CO2
12 + 32 = 44gm12+32 = 44gm

Mass of Reactants = Mass of Products

Read Full Article on Law of Conservation of Mass – Law of conservation of mass

2. Law of Definite Proportions

law of definite proportions

In simple terms, we can say that irrespective of its source, origin, or its quantity, the percent composition of elements by weight in a given compound will always remain the same.

For example, a sample of pure water from various sources or any country is always made up of only hydrogen and oxygen. These elements are always in the same fixed ratio of 1:8 by mass. We can prepare a sample of carbon dioxide in the laboratory.

We can do this in various ways like :

  • Heating limestone.
  • Burning coal in the air.
  • The action of dilute hydrochloric acid on marble.
  • Heating sodium carbonate.

However, we will always find that it contains the same elements, carbon, and oxygen, in the same fixed ratio of 3:8 by mass.

Example

CO2 -> C : OH2O -> H: O
12: 322: 16
3: 81: 8

Limitation

  • It is not applicable if an element exists in different isotopes which may be involved in the formation of the compound. The elements may combine in the same ratio but the compounds formed may be different.

Read Full Article on Law of Definite Proportion – Law of Definite Proportion

3. Law of Multiple Proportions

law of multiple proportions

This law states that if two elements combine to form more than one compound, the masses of these elements in the reaction are in the ratio of small whole numbers.

Discovery

This law was given by Dalton in the year 1803.

Examples

The followings are examples

Example-1

Carbon combines with oxygen to form two compounds namely carbon dioxide and carbon monoxide.

In carbon dioxide, 12 parts by mass of carbon combine with 32 parts by mass of oxygen while in carbon monoxide, 12 parts by mass of carbon combine with 16 parts by mass of oxygen.

The masses of oxygen combined with a fixed mass of carbon in carbon monoxide and carbon dioxide are 16 and 32.

These masses of oxygen bear a simple ratio of 16:32 or 1:2 to each other.

Example-2

Taking another example of the Compounds of Sulphur and oxygen, we see something similar. The element Sulphur also forms two oxides Sulphur dioxide and Sulphur trioxide. In Sulphur dioxide, 32 parts by mass of Sulphur combine with 32 parts by mass of oxygen.

On the other hand, in Sulphur trioxide, 32 parts by mass of Sulphur combines with 48 parts by mass of oxygen. The masses of oxygen combined with the fixed mass of sulfur in the two oxides are 32 and 48.

These bear a simple ratio of 32:48 or 2:3 to each other.

Example-3
NO14:1628: 32
NO214:3228: 64
N2O428:6428: 64
N2O528:8028: 80

Now, ratio of oxygen = 32: 64: 64: 80
= 2: 4: 4: 5

CO12: 16
CO212: 32

Now the ratio of Oxygen =16: 32 = 1: 2

PO216: 32
PO516: 80

Now Ratio of O = 32: 80 = 2: 5

Read Full Article on Law of Multiple Proportion – Law of Multiple Proportion

4. Law of Reciprocal Proportion

law of reciprocal proportions laws of chemical combination

When two elements combine separately with a fixed mass of the third element then the ratio in which they do so is either the same or whole number multiple of the ratio in which they combine with each other.

It states that “If two different elements combine separately with the same weight of a third element, the ratio of the masses in which they do so are either the same or a simple multiple of the mass ratio in which they combine.

Discovery

The law of reciprocal proportions was proposed in essence by Richter, following his determination of neutralization ratios of metals with acids. This law of reciprocal proportions was proposed by Jeremias Ritcher in 1792.

Example

Sulfur and carbon both form compounds with hydrogen. In methane 12g of carbon react with 4g of hydrogen.

In hydrogen sulfide, 32g of sulfur reacts with 2 g of hydrogen (i.e. 64g of S for 4g of hydrogen). Sulfur and carbon form a compound in which the C: S ratio is 12:64 (i.e. CS2).

Read Full Article on Law of Reciprocal ProportionLaw of Reciprocal Proportion

5. Gay Lussac’s Law of Gaseous Volumes

gay lussac's law

This law states that when gases are produced or combine in a chemical reaction, they do so in a simple ratio by volume given that all the gases are at the same temperature and pressure.

  • This law can be considered as another form of the law of definite proportions.
  • The only difference between these two laws of chemical combination is that Gay Lussac’s Law is stated with respect to volume while the law of definite proportions is stated with respect to mass.

Discovery

In 1808, Gay Lussac gave this law based on his observations.

Examples

Some examples are listed below

Example-1: A simple example to prove Gay Lussac’s law is that of hydrogen and chlorine.

1 volume of hydrogen and 1 volume of chlorine always combine to form two volumes of hydrochloric acid gas. The ratio between the volumes of the reactants and the product in this reaction is simple, i.e., 1:1:2.

Example-2:

1 N2 + 3H2 -> 2NH3 (Haber’s Process)

Ratio 1:3. So 100 ml of Nitrogen combines with 300 ml of oxygen to form 200ml of Ammonia

H2 + I2 -> 2HI (Hydrogen Iodide)

Ratio 1:1. So 100 ml of hydrogen combines with 100 ml of Iodine to form 200ml of Hydrogen Iodide.

Read Full Article on Gay Lussac’s Law – Gay Lussac’s Law

6. Avogadro’s Law

Avogadro's law

It stated that under the same conditions of temperature and pressure, an equal volume of all the gases contains an equal number of molecules.

This implies that 2 liters of hydrogen will have the same number of molecules as 2 liters of oxygen given that both the gases are at the same temperature and pressure.

This law states that ‘Under same conditions of temperature and pressure, an equal volume of all the gases contain an equal number of molecules.’

Discovery

Avogadro proposed this law in the year 1811.

Example

Two liters of hydrogen will have the same number of molecules as two liters of oxygen given that both the gases are at the same temperature and pressure. Avogadro proposed this law in the year 1811.

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