According to scientists, there are more than 350,000 chemical compounds, including chemical mixtures, that have been registered for use and production so far. You must have studied a couple of them in your school. But have you heard about the different types of formulas in chemistry? Which formula is an empirical formula? Do you know what is the empirical formula of the phosphorus selenide? What is the empirical formula for phosphorus? Continue reading to know about them.
1. What is Chemical Formula?
A formula stating the types and number of atoms that are present in the molecule of a substance is known as a chemical formula. The formula has an element symbol that represents the type of atoms. The number of atoms is represented by a subscript after the element symbol. For example,
- The molecular formula of a molecule of Hexane is C6H14 which means it has 6 atoms of C and 14 atoms of H. These numbers written with the alphabet are the subscript and the alphabet is the element symbol of the compound.
- Table salt has the chemical formula NaCl which means there is 1 atom of sodium and 1 atom of chlorine.
2. What are Different Types of Chemical Formulas?
There are 4 types of chemical formulas, namely empirical structure, molecular formula, condensed chemical formula, and structural formula. Today we will be discussing in detail the empirical formula.
- Empirical Formula: The representation of the simplest whole number ratio of a chemical compound is known as the empirical formula. It does not mention the number of atoms or the arrangement of atoms in the compound. Before moving ahead to learn about what is the empirical formula of the phosphorus Selenide, it was better to get a glimpse of what is the empirical formula.
- Molecular Formula: The formula which states the exact number of atoms present in a compound is known as the molecular formula. Since it represents the actual figure of atoms, it is also known as the true formula. For example, the molecular formula of propane is C6H10. Here, you can see clearly that there are 4 atoms of C and 10 atoms of H.
- Condensed Chemical Formula: The formula that simply states the chemical bonds and formulas of functional groups in shorthand notation is known as the condensed chemical formula. It omits the symbols. The atoms are listed in the order of their appearance in the molecular structure. For example, the molecular formula of hexane is C6H14, but its condensed formula is CH3(CH2)4CH3.
- Structural Formula: As its name suggests, this formula shows you how many atoms are in the compound and ignores their arrangement and bond, while it shows only the chemical bond. Some structural formulas indicate the 2-dimensional structure, while others show the 2-dimensional structure.
3. Which Formula is an Empirical Formula?
Here I have broken down the explanation into points for a better understanding before you move toward, what is the empirical formula of the phosphorus Selenide.
- The simplest formula of a chemical compound which is defined as the ratio of subscripts of the smallest whole number that is present in the elements of the formula is termed an empirical formula. Since it is representing the simplest version, it is also termed a simple formula.
- This formula gives you information about the number of atoms in the compound.
- The formula of the smallest integer subscript is the empirical formula of a subscript.
4. How to Calculate the Empirical Formula?
If you have certain data, and you need to find what is the empirical formula of the phosphorus selenide or of any compounds, you can follow these steps, as mentioned in the example here. Sometimes, the data can be in percentages or grams. In such a case, you have to convert the data given in percentages into grams and then begin the calculation.
For example, you have 13.5% calcium, 10.8% oxygen, and 0.675% of hydrogen, and you are asked to find their empirical formula.
You will begin with a simple conversion of percentages into grams. 13.5% will be written as 13.5 grams of calcium, 10.8% oxygen will be 10.8 grams of oxygen, and 0.675% will become 0.675 grams of hydrogen.
Once you have data in grams, convert them into moles by looking for their atomic numbers in the periodic table and then marking their atomic mass. For the above data, it will be,
40.1 grams/mole for calcium
16.0 grams/mole for oxygen
1.01 grams/mole for hydrogen
Therefore, the calculation will be:
- Calcium (Ca): 13.5 grams Ca × (1 m mol Ca/40.1 Ca) = 0.337 mol Ca
- Oxygen (O): 10.8 grams O × (1 mol O / 16.0 grams O) = 0.675 mol O
- Hydrogen (H): 0.675 grams H × (1 mol H / 1.01 grams H) = 0.668 mol H
Now, each mole obtained will be divided by the smallest mole in the series and the answer will be rounded to the next or nearest whole number. These numbers will be your subscripts, to be written with the elements.
- Calcium (Ca): 0.337 mol Ca / 0.337 = 1.00 mol Ca
- Oxygen (O): 0.675 mol O / 0.337 = 2.00 mol O
- Hydrogen (H): 0.668 mol H / 0.337 = 1.98 mol H, rounds up to 2.00
Now, you can write the empirical formula for the compound with the above whole numbers obtained. The empirical formula will be CaO2H2. (See What is Sand Chemical Name?)
5. What is the Empirical Formula of the Phosphorus Selenide?
This is an obscure group of compounds whose empirical formula is P4Se3. You can obtain what is the empirical formula of the Phosphorus Selenide using the same method by which we have calculated in the above example. It shows that there are 4 molecules of Phosphorus (P) and 3 molecules of Selenide (Se). (See How many Oxygen Atoms are in SiO2?)
6. What is the Empirical Formula for Phosphorus?
The empirical formula for phosphorus is P2O5. This clearly indicates that there are 2 molecules of phosphorus (P) and 5 molecules of Oxygen (O). (See What is the Number in Periodic Table of Elements H2O?)
7. What is the Significance of Empirical Formula?
With an easy method of calculation, empirical formulas are important due to the following reasons:
- An empirical formula mentions the names of all the elements present in the compound.
- The empirical formula of a substance is equal to the formula mass of the substance. Further, the formula mass is equal to the atomic masses for all the atoms present in the empirical formula.
- An empirical formula for a compound provides you with the whole number ratio in its simplest form. This simple form consists of all the elements and the number of atoms of respective elements in the compound.
So, today you got to know which formula is an empirical formula. Also, you learned about what is the empirical formula of the phosphorus Selenide and how to understand it. Along with learning the method of finding the empirical formulas, you can easily calculate what is the empirical formula for phosphorus. Now try finding the empirical formula for other compounds. (See What are the Components of Water?)