How to calculate moles from given mass of a substance?

How to calculate moles from given mass of a substance?Practice questions/worksheet for IB and IGCSE students

Mole(n)= Mass of a substance(m)/ Molar mass(Mr)

so moles of a substance , n= m / Mr

The first question is solved for you.

For calculating Molar mass, you need to add the relative atomic masses of all the atoms in a 

compound or ion. For example Mr of Na₂O = (23x2)+16 = 62 ,

because  Ar( relative atomic mass) of Na=23,

Ar( relative atomic mass) of O= 16

so  moles of 100 g Na₂O= 100/ 62= 1.61 moles

Calculate number of moles in 50 g of Na₂O

Calculate number of moles in 100 g of H₂O

Calculate number of moles in 25 g of NaOH

Calculate number of moles in 75 g of MgO

Calculate number of moles in 65 g of Mg(OH)₂

Calculate number of moles in 15 g of Li₂O

Calculate number of moles in 85 g of HCl

Calculate number of moles in 33 g of LiCl

Calculate number of moles in 48 g of MgCl₂

Calculate number of moles in 77 g of P₄O₁₀

Calculate number of moles in 43 g of H₃PO₄

Calculate number of moles in 94 g of Cl₂O₇

Calculate number of moles in 69 g of HClO₄

Calculate number of moles in 86 g of SO₂

Calculate number of moles in 39 g of H₂SO₃

Calculate number of moles in 68 g of SiO₂

Calculate number of moles in 74 g of Al₂O₃

Calculate number of moles in 116 g of H₂SO₄

Calculate number of moles in 5k g of Al₂(SO₄)₃

Calculate number of moles in 2.5 g of CO

Calculate number of moles in 10 g of NO

 Calculate number of moles in 88 g of CO₂

Calculate number of moles in 56 g of N₂

Calculate number of moles in 235 g of 𝐶𝐻₄

Calculate number of moles in 64 g of 𝑂₂

Calculate number of moles in 45 g of 𝐶₆𝐻₁₂𝑂₆

Calculate number of moles in 99 g of 𝑆𝑂𝐶𝑙₂

Calculate number of moles in 235 g of 𝐹𝑒𝐶𝑙_3.

How to calculate mass from given moles of a substance or compound?

How to calculate mass from given moles of a substance or compound? Practice questions/worksheet on mass to mole

Mole(n)= Mass of a substance(m)/ Molar mass(Mr)

so mass of a substance , m= nx Mr

The first question is solved for you.

For calculating Molar mass, you need to add the relative atomic masses of all the atoms in a 

compound or ion. For example Mr of Na₂O = (23x2)+16 = 62 ,

because  Ar( relative atomic mass) of Na=23,

Ar( relative atomic mass) of O= 16

so  mass of 1.5  moles of Na₂O= 1.5x62= 93 g

Calculate mass  in  1.5 moles of Na₂O

Calculate mass  in  2.5 moles of H₂O

 Calculate mass  in  3.5 moles of NaOH

Calculate mass  in  0.5 moles of MgO

 Calculate mass  in  4.5 moles of Mg(OH)₂

Calculate mass  in  0.5 moles of Li₂O

Calculate mass  in  2.5 moles of HCl

Calculate mass  in  6.5 moles of LiCl

Calculate mass  in  1.5 moles  of MgCl₂

Calculate mass  in  5.5 moles of P₄O₁₀

Calculate mass  in  0.5 moles of H₃PO₄

Calculate mass  in  7.5 moles of Cl₂O₇

Calculate mass  in  1.15 moles of HClO₄

Calculate mass  in  1.25 moles of SO₂

Calculate mass  in  1.35 moles of H₂SO₃

Calculate mass  in  1.45 moles of SiO₂

Calculate mass  in  1.55 moles of Al₂O₃

Calculate mass  in  10.5 moles of H₂SO₄

Calculate mass  in  12.5 moles of Al₂(SO₄)₃

Calculate mass  in  1.35 moles of CO

Calculate mass  in  1.25 moles of NO

 Calculate mass  in  1.45 moles of CO₂

Calculate mass  in  1.55 moles of N₂

Calculate mass  in  1.55 moles of 𝐶𝐻₄

Calculate mass  in  1.25 moles  of 𝑂₂

Calculate mass  in  1.5 moles  of 𝐶₆𝐻₁₂𝑂₆

Calculate mass  in  1.58 moles  of 𝑆𝑂𝐶𝑙₂

 Calculate mass  in  1.50 moles  of 𝐹𝑒𝐶𝑙_3.

What is Empirical formula? How to determine it?

What is Empirical formula? How to determine it?and Determining Molecular formula:

Empirical formula:  Chemical Formula with simplest ratio of atoms of a compound.

Molecular formula: Chemical Formula with definite number of atoms of a compound.

Example:  

C₆H₆ is the molecular formula of benzene.

CH is the simplest ratio of atoms of C₆H₆

Molecular formula = n X Empirical formula 

where n=Molecular formula mass/Empirical formula mass

  molecular formula mass of C₆H₆ is 78 g/mol

Empirical formula mass of CH is 13 g/mol

n= 78/13= 6

Molecular formula = n X Empirical formula = 6 X CH= C₆H₆

Step 1: Write the element symbols along with % given. Consider % as mass in gram.

Step 2: Divide the given mass of each element by relative atomic mass of that element.

( mole=mass/molar mass) so you get moles of each element here.

Step 3: Divide the moles of each element by the smallest moles obtained in step 2.

Step 4: Use the obtained values as number of atoms per element in empirical formula.

Note : if you did not get the whole number values, do not simply round off the values but multiply by suitable integers to make the value whole number. Example if you get 2.5, do not round simply to 3 but multiply 2.5 by 2 to get 5 which is a whole number.

Worked Problem:   A compound has 44.09 % iron and rest chlorine. Determine its empirical formula.  If the molar mass of the compound is 127 g/mol, determine its Molecular formula as well.

Solution: 

Step1	Iron(Fe)=44.09	Chlorine(Cl)=100-44.09=55.91
Step2	44.09/56	55.91/35.5
Step3	0.79/0.79=1	1.57/0.79= 1.98=2
Step4	1	2

So the empirical formula is FeCl₂  so now to find out molecular formula, 

use Molecular formula = n X Empirical formula where n=1

hence Empirical formula = Molecular formula

Practice questions:  

1.       A binary oxide has 74.19 % sodium and rest oxygen. Determine its empirical formula.  If the molar mass of the compound is 62 g/mol, determine its Molecular formula as well.

2.       A compound has 43.39 % sodium, 11.32% carbon  and rest oxygen. Determine its empirical formula.  If the molar mass of the compound is 106 g/mol, determine its Molecular formula as well.

3.       A compound has 34.46 % iron and rest chlorine. Determine its empirical formula.  If the molar mass of the compound is 162.5 g/mol, determine its Molecular formula as well.

4.       A binary oxide has 43.66 % phosphorus and rest oxygen. Determine its empirical formula.  If the molar mass of the compound is 284 g/mol, determine its Molecular formula as well.

5.       A compound has 40 % carbon, 6.6% hydrogen  and rest oxygen. Determine its empirical formula.  If the molar mass of the compound is 180 g/mol, determine its Molecular formula as well.

How to calculate Molar mass and names practice questions

Calculate molar mass of the following compounds and formula units and write their names.

1.       Na2O

2.        H2O

3.        NaOH

4.        MgO

5.        Mg(OH)2

6.       Li2O

7.        HCl

8.       LiCl

9.       MgCl2

10.   P4O10

11.   H3PO4

12.   Cl2O7

13.   HClO4

14.   SO2

15.   H2SO3

16.   SiO2

17.   OH−

18.   SiO32−

19.   Al2O3

20.   H2SO4

21.   Al2(SO4)3

22.   Al (OH)4−

23.   CO

24.   NO

25.    CO2

26.    N2

27.   𝐶𝐻4

28.   𝑂2

29.   𝐶6𝐻12𝑂6

30.   𝑆𝑂𝐶𝑙2

31.    𝐹𝑒𝐶𝑙3.

Definition of Mole and it’s relationship with mass

 Definition of Mole and it’s relationship with mass

 It is an amount of a substance which contains as many particles as there are in

12 g of C-12 isotopes that is  6.022X10²³

6.022X10²³ is known as Avogadro's number.

For example: 1 mole atoms = gram atomic mass = 6.022X10²³ atoms

                 
 1 mole oxygen atoms = gram atomic mass of oxygen =16 g = 6.022X10²³ atoms

1 mole molecules  = gram molecular  mass = 6.022X10²³  molecules

Example -

1 mole oxygen  molecules  = gram molecular  mass of oxygen =32 g =

6.022X10²³ oxygen molecules

1 mole ions  = formula unit mass = 6.022X10²³ ions

Example - 1 mole( SO₄)^2- ions  = formula unit mass of ( SO₄)^2-=96g = 6.022X10²³
  ( SO₄)²ions

The mass (nucleon) number, A, is the sum of the protons and the neutrons. (= 12 for Carbon)

The atomic (proton) number, Z, of an element is the number of protons in the nucleus of the atom. In the neutral atom it is equal to the number of electrons. ( 6 for Carbon)

The Relative Atomic Mass, A(r), is the mass of one atom of an element compared to a scale in which one atom of carbon-12 has a mass of 12.0000.

The Relative Molecular Mass, M(r), is the ratio of the mass of one molecule of a substance to the mass of one atom of carbon-12. It is calculated by adding the relative atomic masses of all the atoms of all elements in the molecule.

Relative molecular mass, M(r), or  relative formula mass (for those compounds that do not exist as molecules) is calculated by adding together the Relative Atomic MassA(r) ‘s of the elements in the molecular formula.

Use of State symbols in Chemical Equations

Use of State symbols in Chemical Equations

Use of state symbols is very key to get marks in IB diploma exams. It is not difficult to use state symbols in chemical equations.
What is state symbols? 
State symbols are symbols used to represent the physical state of reactants and products in a chemical equation.

Example:

White solid magnesium Oxide is formed when Magnesium metal ribbon is burned in air( oxygen gas).

2Mg(s) + O2(g)    à 2 MgO(S) 

Try to write the state symbols of the following equations:

Ag⁺   + X⁻   → AgX(s)

Na₂O + H₂O → 2NaOH

 MgO + H₂O → Mg(OH)₂

Li₂O(s) + 2HCl → 2LiCl  + H₂O

MgO + 2HCl  → MgCl₂ + H₂O

P₄O₁₀+ 6 H₂O→ 4H₃PO₄

Particulate nature of matter

Particulate nature of matter

1.1 Introduction to the particulate nature of matter and chemical change
Matter : Anything which occupy space and has a mass is called matter.
Example: Air, Water, Oil, wood , Iron etc

Types of matter:

matter is basically of three types:

Solid: Particles are held very close to each other in solids in a regular order and there is very little freedom of movement due to strong attractive forces between particles.

 As a result, Solids have definite volume and definite shape.

 Question: Write few  examples of solids.

Challenge: Is Clay solid or liquid? Why is it solid or liquid?

Liquid: Particles are close to each other but they can move around due to weaker attractive forces 

 between particles compared to solid particles.

              As a result, Liquids have definite volume but do not have definite shape. 

They acquire the shape of the container in which they are kept.

Question: Name 5 liquids. Is toothpaste a liquid?

Gas : Particles are far apart their movement is easy and fast due to negligible attractive forces between particles. Gases have neither definite volume nor definite shape. They completely occupy the space in the container in which they are placed.

Question: Name 5 gases. 

Challenge: Is gas or vapour same?

 Why  or why not?

nter-conversion of States of matter:

The states of matter are inter-convertible by changing the conditions of temperature and pressure. 

On heating, a solid usually changes to a liquid, and the liquid on further heating changes to gas or vapour. 

In the reverse process, a gas on cooling liquifies to a liquid and the liquid on further cooling freezes to the solid.

Fun activity on Periodic table Elements

Fun activity on Periodic table Elements

This is a fun activity for periodic table and can be used as starter.

Cartoon of Elements

Use periodic table to identify group of cartoons. You can use first or first two letters also to find the name.

Chotabhimg–

Carbon, Hydrogen, Hydrogen, Oxygen, Tantalum, Boron, Hydrogen, Iodine, Magnesium

Nobita-

Nobelium, Bismuth, Tantalum

Shinchan-

 Sulphur, Hydrogen, Iodine, Nitrogen, Carbon, Hydrogen,

Shiva-

Sulphur, Hydrogen, Iodine, Vanadium

Krish-

Krypton, iodine, sulphur, hydrogen

Inter-conversion of States of matter

Inter-conversion of States of matter

The states of matter are inter-convertible by changing the conditions of temperature and pressure. On heating, a solid usually changes to a liquid, and the liquid on further heating changes to gas or vapour. In the reverse process, a gas on cooling liquifies to a liquid and the liquid on further cooling freezes to the solid.

States of Matter in Chemistry

States of Matter in Chemistry

 Matter  exists in three physical states:
Solid: Particles are held very close to each other in solids in a regular order and there is very little freedom of movement due to strong attractive forces between particles.As a result, Solids have definite volume and definite shape.

Liquid: Particles are close to each other but they can move around due to weaker attractive        forces between particles compared to solid particles. As a result, Liquids have definite volume but do not have definite shape. They acquire the shape of the container in which they are kept.

Gas : Particles are far apart their movement is easy and fast due to negligible attractive forces

 between particles. Gases have neither definite volume nor definite shape. They completely

 occupy the space in the container in which they are placed.

States of Matter