__Formulas in brief__* –*

**Mass = Molar mass x Number of moles**

**Number of moles = Given number of particles / Avogadro number****Number of particles = (Given mass / molar mass) x Avogadro number**(from 1 and 2)- If one carbon atom has a mass of 12 atomic mass units and one magnesium atom has a mass of 24 atomic mass units, then as a magnesium atom is twice as heavy as a carbon atom. It follows that this ratio will be maintained for any number of atoms.
- Equal masses of carbon and magnesium contain different numbers of atoms.

6 g of carbon contains 6 / 12 moles of carbon = 0.5 moles

6 g of magnesium contains 6 / 24 moles of magnesium =0.25 moles

- 1 mole = 6.022 x 10
^{23}atoms or molecules or formula units of that substance.

1 mole of water (H_{2}O)contains 2 moles of hydrogen atoms and 1 mole of oxygen atoms. It is a simple matter of multiplying the moles of the compound by the atoms or ions that make it up.

**Read more –**

What is Matter? What is its Characteristics?

Problems based on Law of Conservation of Mass

Law of Definite Proportions / Constant Composition

Problems based on law of definite proportions or constant composition

Mole Concept – Importance and formulas

Quiz – Mole Concept and Stoichiometry – 1

** Problem based on formula no. – 1
Mass = Molar mass x Number of moles
**Calculation of mass from mole of any

*fundamental unit like atom, molecule*and vice – versa.

**Note that if it is not mention atom or molecule before mole, it always means one mole of that substance in its natural form. **

** **

**Example 1- **How many grams are there in 5.5 mol of sulphur?

**Solution – **For converting mass into mole and vice versa, we always need the molar mass.

Molar mass of sulphur = 32.0 g mol^{–1}

Number of moles of sulphur = 5.50 mol** **

Therefore, mass of sulphur (in grams) = molar mass x number of moles

= 5.50 mol × 32.0 *g* mol^{–1}= **176.0 g sulphur**

**Example 2- **Calculate number of moles present in 64 g of oxygen.

**Solution – **Molar mass of oxygen = 32 g mol^{–1}

Oxygen in natural form will be molecular oxygen, O2

Therefore, number of moles of oxygen = 64 g / 32 g mol^{–1} = **2.0 moles**

** **

**Example 3- **Calculate the number of moles present in 108 g of aluminium.

**Solution – ** Atomic mass of Al = 27gm

So, 27g of aluminium = 1 mole of aluminium

Or, by using formula , Number of moles = given mass / atomic mass

Or, Number of moles = 1/27 x 108 = ** **4 moles of aluminium** **

Thus, 108g of aluminium = **4 moles of aluminium **

**Example 4 – **Calculate the mass of 0.5 mole of iron.

**Solution – **Atomic mass of iron = 55.9 g

Mass of the 1 mole of iron = 55.9 g

Or, by using formula, mass = atomic mass x number of moles

Mass of the 0.5 mole of iron = 55.9 x 0.5 g = **27.95 g**

**Now, Check your understanding –**

**1. Atomic number (Z) of Iron, Fe is 26, Atomic mass 56.**

Using the above information answer the following-

(a) 1 mole of iron weighs __________ grams.

(b) 7.4 moles of iron weighs ________________ grams.

2. 1 litre of an aqueous solution of NaCl contains 117g of the dissolved salt. Calculate the number of moles of the solute in the solution. (Na = 23u , Cl = 35.5)

3. Two bottles A and B contain 1000 ml. water solutions of 60g NaOH and 117g NaCl respectively. Which bottle has more concentrated solution?

** Problem based on formula no. – 2
Number of moles = Given number of particles / Avogadro number
**Calculation of mole from number of particles and vice – versa.

**Example 5 – **Calculate the number of moles of 24.088 x 10^{23} numbers of sodium atom.

**Solution – **Given number of particles = 24.088 x 10^{23}

Avogadro number = 6.022 x 10^{23}

Number of moles = Given number of particles / Avogadro number**
= **24.088 x 10

^{23}/ 6.022 x 10

^{23}

** = 4 moles**

Example 6 – Calculate the number of particles in 0.5 moles of N atom.

**Solution – ** Number of moles = 0.5 moles

Avogadro number = 6.022 x 10^{23}

Number of particles = Number of moles x Avogadro number**
= **0.5 x 6.022 x 10

^{23}

** = 3.011 x 10**^{23}

**Now, Check your understanding –**

**Atomic number (Z) of Iron, Fe is 26, Atomic mass 56.**

Using the above information answer the following-

(a) 7.4 moles of iron contains ________________ atoms.

(b) 1.2 x 10^{24 }atoms of iron would be _____________ moles of iron.

*Problem based on formula no. – 3*

**Number of particles = (Given mass / molar mass) x Avogadro number
**Calculation of number of particles from mass and vice – versa.

**Example 7 – **Calculate the number of molecules in 22 g of *CO*_{2}

**Solution – ** Gram molecular mass or molar mass of CO_{2} = 44 g

Number of particles = (Given mass / molar mass) x Avogadro number = ( 22 g / 44 g ) x 6.022 x 10^{23} = **3.011 x 10**^{23}** ****molecules**

**Example 8 – **Calculate the mass of 18.066 x 10^{23 }molecules of SO_{2}

**Solution – ** Gram molecular mass or molar mass of SO_{2} = 64 g

Mass = (Number of particles x molar mass) / Avogadro number

= (18.066 x 10^{23} x 64) / 6.022 x 10^{23}

** = 192 g**

Example 9 – Calculate the mass of glucose in 2 x 10^{24} molecules.

**Solution – ** Gram molecular mass or molar mass of glucose = 180 g

** **Mass = (Number of particles x molar mass) / Avogadro number

= (2 x 10^{24} x 180) / 6.022 x 10^{23}

** = 597.8 g
**

**Example 10 –**How many atoms are there in 24 g of carbon?

**Solution – ** 24 g of carbon = 24 / 12 moles = 2 moles

1 mole of atoms = 6.022 x 10^{23}

Therefore 2 moles of carbon contains 2 x 6.022 x 10^{23} atoms = **1.204 x 10**^{24}** atoms. **

** ****Now, Check your understanding –**

**Atomic number (Z) of Iron, Fe is 26, Atomic mass 56.**

Using the above information answer the following-

(a) 1 gram of iron contains ________________ atoms.

(b) 1 atom of iron weighs _________________ grams.

**Thus, One mole of oxygen stands for –
**1. 6.022 x 10

^{23}molecules of oxygen

2. 2 x 6.022 x 10

^{23}atoms of oxygen

3. 1 gram molecule of oxygen

4. 2 gram atoms of oxygen

5. 32 grams oxygen

Don’t Miss –

Pingback: Mole Concept – Concept, Importance and Formulas – Freakgenie

Pingback: How do you Write Chemical Formula for an Ionic Compound? – Freakgenie

Pingback: ATOMS AND MOLECULES – NECRT TEXT BOOK Questions Solutions – Freakgenie

Pingback: Problems based on Law of Definite Proportions / Constant Composition – Freakgenie

Abd Assalam BushiraLove it.Am progressing slowly

adminThanks. Please try – Quiz based on Mole Concept and Stoichiometry – 1

adminhttps://freakgenie.comquiz-mole-concept-and-stoichiometry-1/

MounikaSuper

adminThanks. Please try – Quiz based on Mole Concept and Stoichiometry – 1

adminhttps://freakgenie.comquiz-mole-concept-and-stoichiometry-1/

UmbulQuiz was too good but due to some reasons I didn’t saw the results of the quiz or I think the website didn’t make me to see the result

adminThanks and keep visiting.

It should be available in your email. Also you can find the answers with result after submitting your answers.

Neha rathodBut it would be great if you guys provided with advance level jEe questions. Btw thank you

DashmeetSuperbbb love it

PreritI liked it.

adminThanks. Keep visiting.

ShambhawiReally nice