IGCSE CHEMISTRY-EXTRACTION OF METALS
IGCSE CHEMISTRY-EXTRACTION OF METALS
Showing posts with label igcse. Show all posts
Showing posts with label igcse. Show all posts
Thursday, 19 February 2026
Thursday, 31 July 2025
(HANDOUT) IGCSE Chemistry-Redox Reactions
REDOX REACTIONS
- Redox stands for reduction oxidation.
- Redox reaction, also called oxidation reduction reaction, is a chemical reaction in which one substance is reduced and another is oxidised simultaneously.
- Oxidation and reduction of substances occur simultaneously. As one substance is reduced the other is oxidised.
- An oxidising agent is a substance that causes the oxidation of the other substance. Therefore, the substance that is reduced in a reaction is the oxidising agent.
- A reducing agent is a substance that causes the reduction of the other substance. For example, the substance that is oxidised in a reaction is the reducing agent.
OXYGEN IN REDOX REACTION
- Oxidation is the gain of oxygen by the substance. A substance that has gained oxygen is said to be oxidised.
- Reduction is the loss of oxygen by the substance. A substance that has lost oxygen is said to be reduced.
HYDROGEN IN REDOX REACTION
- Oxidation is the loss of hydrogen by the substance. A substance that has lost hydrogen is said to be oxidised.
- Reduction is the gain of hydrogen by the substance. A substance that has gained hydrogen is said to be reduced.
ELECTRONS IN REDOX
- Oxidation is the loss of electrons. A substance that loses electrons is oxidised.
- Reduction is the gain of electrons. A substance that gains electrons is reduced.
- The reaction below shows a redox reaction involving the gain and loss of electrons.
OXIDATION NUMBER
- Oxidation number, also called oxidation state, is the number of electrons an atom gains or losses in a chemical combination.
REDOX REACTION PRESENTATION
REDOX REACTIONS
- Redox stands for reduction oxidation.
- Redox reaction, also called oxidation reduction reaction, is a chemical reaction in which one substance is reduced and another is oxidised simultaneously.
- Oxidation and reduction of substances occur simultaneously. As one substance is reduced the other is oxidised.
- An oxidising agent is a substance that causes the oxidation of the other substance. Therefore, the substance that is reduced in a reaction is the oxidising agent.
- A reducing agent is a substance that causes the reduction of the other substance. For example, the substance that is oxidised in a reaction is the reducing agent.
Monday, 24 July 2023
Sunday, 4 April 2021
Sunday, 31 January 2021
Quiz-Counting Atoms (IGCSE CHEMISTRY)
QUIZ – COUNTING ATOM
NAME/# : __________________________
DAY, DATE : __________________________
- Calculate the volume of the 3.2 g of sulphur trioxide gas at r.t.p condition and at s.t.p condition
Ans:
- A sample of carbon monoxide gas, CO, has volume of 6 dm3 at r.t.p.
- How many moles of the gas are there in the sample?
Ans:
- How many particles are there
Ans:
- What is the mass of the sample?
Ans:
- An unknown compound is analyzed and found to consist of 24.3 % carbon, 4.1 % hydrogen, and 71.6 % chlorine. If the molecular mass of the compound is 98.8, what is the molecular formula of the compound?
Ans:
- The element boron forms several compounds that contain only boron and hydrogen. A sample of one of these compounds weighing 56 g was found to contain 44 g of boron.
- Find the ratio of the number of hydrogen atoms to the number of boron atoms in the compound.
Ans:
- The rtelative molecular mass of the compound is 28. Write the chemical formula for this compound of boron and hydrogen.
Ans:
- Hydrated sodium carbonate has the formula Na2CO3.nH2O. on strong heating, Hydrated sodium carbonate decomposes completely into water and anhydrous sodium carbonate, CuSO4. The formula of Hydrated sodium carbonate was found by the following procedure.
A mass of Hydrated sodium carbonate was heated strongly in a crucible until decomposition was complete.
the following result was obtained.
Mass of empty crucible = 11.50 g
Mass of crucible + hydrated copper(II) sulphate = 17.22 g
Mass of crucible + anhydrous copper(II) sulphate = 13.62 g
- Suggest how you could find out when the decomposition of Hydrated sodium carbonate is complete
Ans:
- Calculate the mass of water evaporated in the decomposition, and the number of moles of the water.
Ans:
- Calculate the mass of anhydrous sodium carbonate produced in the decomposition, and the number of moles of Na2CO3
Ans:
- Find the value of n in the formula
Ans:
Counting Atoms - Moles (IGCSE CHEMISTRY) slide presentation
CH. 9 COUNTING ATOM
KKCS International Program
Chemistry IGCSE
Mr. Markus
MOLE CONCEPT
The mole is defined as the amount of substance that contains as many particles as the number of carbon atoms, in exactly 12 grams of carbon-12
The number is equal to 6.0 x 10 23 particles (Avogadro’s number)
The mole is abbreviated as mol
The mole is a counting unit used in chemistry to deal with atoms, molecules and ions.
Example:
1 mole of carbon atoms = 6.0 x 10 23 C atoms
1 mole of ammonia molecules = 6.0 x 10 23 NH3 molecule
1 mole of sodium ions = 6.0 x 10 23 Na+ ions
To change the number of particles to the number of moles :
number of moles = number of particles
6.0 x 10 23
To change the number of moles to the number of particles
Number of particles = (number of moles) X (6.0 x 10 23 )
EXERCISE
A sample of sodium contains 3.0 x 1020 Calculate the number of moles of sodium.
Determine the number of molecules in 0,5 moles of carbon dioxide.
How many H atoms are in 0.80 moles of hexane. C6H14?
How many NH4+ ions are in 1.5 moles of (NH4)3PO4?
How many molecules are there in 0.2 mole of sulphur dioxide, SO2? How many atoms are present?
MASS MOLAR
The mass in gram of 1 mole of substance is caleed its molar mass
The molar mass of any substance is always equal to its relative formula mas in gram, :
a. The mass of 1 mole of atom is equal to its relative atomic mass in grams/Ar
b. The mass of 1 molelecules is equal to its relative molecular mass in grams/Mr
c. The mass of 1 mole of units of ionic compound is wqual to its relative formula mass in grams
Ex. 1
Relative atomic mass of magnesium, Mg = 24
Hence, mass of 1 mole of Mg atoms = 24 g,
i.e. Molar mass Mg = 24 g/mol
Ex.2
Relative molecular mass of Ammonia,
NH3 = 14 + 3(1) = 17
Hence, mass of 1 mole of NH3 molecules = 17 g
i.e. Molar mass of NH3 = 17 g/mol
Ex.3
Relative formula mass of nitrate ion,
NO3- = 14 + 3(16) = 62
Hence, mass of 1 mole of NO3- ions = 62 g
i.e. Molar mass of No3- = 62 g/mol
To convert moles to mass, use the following:
mass of substance =
(number of moles of substance) x molar mass of subst.
Mass to moles
number of mole of substance
= mass of substance
molar mass of substance
Example:
Calculate the mass of 2.50 moles of Al atoms
Solution:
Relative atomic mass of Al (Ar Al) = 27.0
Molar mass of Al = 27 g/mol
Mass of 2.50 moles of Al atoms
= (moles) x (molar mass)
= 2.50 mol x 27.0 g/mol
= 67.5 g
Calculate the mass of 1.12 moles of sulphur trioxide molecules.
Calculate the number of moles of molecus in 66 g of carbon dioxide.
Calculate the number of moles Pb(CH3COO)2 in 250 g of lead(II) ethanoate
Calculate the number of moles of each element present in 1 mole of each of these:
a. Sucrose, C12H22O11
b. Calcium phosphate, Ca3(PO4)2
Calculate the mass of 1.12 moles of sulphur trioxide molecules.
Answer:
Mr SO3 = 32+3(16) = 80 g/mol
Mass of SO3 = 1.12 mol x 80 g/mol
= 89.6 g
2. Calculate the number of moles of molecus in 66 g of carbon dioxide.
Ans:
Mr CO2 = 12 + 2(16) = 44 g/mol
Moles of CO2 = 66 g = 1.5 mol
44 g/mol
Calculate the number of moles Pb(CH3COO)2 in 250 g of lead(II) ethanoate
Ans:
Mr Pb(CH3COO)2 = 207 + 4(12) + 6(1) + 4(16)
= 325 g/mol
Moles of Pb(CH3COO)2 = 250 g = 0.769 mol
325 g/mol
4. Calculate the number of moles of each element present in 1 mole of each of these:
a. Sucrose, C12H22O11
Ans: Carbon = 12 moles, Hydrogen = 22 moles, Oxygen = 11 moles
b. Calcium phosphate, Ca3(PO4)2
Ans: Calcium 3 moles, Posphate 2 moles, oxygen 8 moles
5. Calculate the number of moles of each element present in 100 g of each of the following:
a. (NH4)2Cr2O7
b. Na2CO3.10H2O
