Hydrogen ion concentration in a solution and pH scale

pH is the degree of acidity or basicity of a chemical substance in aqueous systems.

In simple terms pH is the power of hydrogen ion or hydronium ion concentration.

It can be calculated by :
pH = - log₁₀[H⁺] or 

pH = - log₁₀[H₃O⁺] 

[ ] square bracket represents the concentration in mol/dm³

Example: If a sample of an acid is found to have[ H⁺]=1X10^-4

Than pH = - log₁₀[1X10^-4]

pH = -[-4 log 10]

pH= 4
If you want to find out [ H⁺] than you can use the following formula: pH = 10^-pH

Chemistry data booklet for IB latest

Chemistry data booklet for IB latest 

Latest Chemistry data booklet for IB diploma chemistry students is of fourth edition and it is for the 2019 and 2020 final IB Diploma students. It is in use since 2016 examinations. Students often uses old data booklets which is not suitable for the latest IB questions as they write to reffer on a particular table number which is not similar in old and new data booklet.
Students should also focus on the content of data booklet because if you are familiar about what is already given in the data booklet, you need not to mug it up.

Chemistry Data booklet

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.

How to prepare for the IB and IGCSE examinations?

How to prepare for the IB and IGCSE examinations?

Examination management plan:

It is not too late to start preparation for coming IB and IGCSE exams. What has happened in past is not a point of thought for now. It is time to gather all your energy and plan for writing exams.

You can focus on following steps to see yourself in a better place during exams:

1. Choose relevant and selective study material like IB and IGCSE textbook, notes, guide books etc.

2. Believe in yourself that you can do it.

3. Make a time table to study all subjects according to your need.

4. Do not focus on one subject only but study all subjects on scheduled time.

5. Make some small points for quick revision. You may prepare flash cards also.

6. Check the IB and IGCSE syllabus of your exam and identify the simpler topics first to study.

7. After covering simple topics you will gain confidence, now start solving past papers and solve only the questions from topics you already covered.

8. Now select one hard topic and divide it in small parts to study one by one. Continue the work till the exams starts.

9. Take healthy diet and keep positive attitude.

10. Do not visit the friends who de motivate you.

During Exam day:

1. Wake up on time and get ready for exam.

2. Do not panic and remain relaxed.

3. Check all necessary stationary like pen, pencil etc

4. Reach the exam room on time and drink water before exam because without water due to dehydration you may get head ach.

5. Read the compulsory instructions given on the question paper and start answering the known questions or easy questions than hard questions.

6. Do not waste too much time on thinking the answer but after finishing the questions you may again work on the unsolved questions.

7. Once you finish the question paper, check the answer sheet once again.

8. Ensure that you have filled all necessary information on answer sheet.

9. After the exam, do not compare the answers with anyone because it will affect your next exam.

10. Start planning and preparing for next exam.