Topics in Chemistry
Chemistry Scheme of Work, SS1 Third Term Chemical Industries: Petrochemicals, Biodegradable, Non-biodegradable Wastes and Pollutants Chemical Industries: Types, Advantages, Disadvantages and Factors affecting Chemical Industries Hydrocarbons: Fractional Distillation of Crude oil and Uses of its Fractions Hydrocarbons: Sources, Classification and Test for Saturated and Unsaturated Hydrocarbons Trioxocarbonates: Preparation, Physical and Chemical Properties, Tests and Uses of Trioxocarbonates Carbon and its Compounds: Oxides of Carbon, Carbon(IV) oxide Carbon and its Compounds: Oxides of Carbon Amorphous Allotropes of Carbon Carbon: Structure and Allotropes of Carbon Salts in Chemistry: Types, Properties, and Uses of Salts Salts in Chemistry, their Classifications, Solubility, Preparations and Colors pH Indicators, Types of Indicators and Importance of pH and pOH Relative Acidity and Alkalinity (pH Scale), and Calculations on pH Bases and Alkalis: Definitions, Classification, Physical and Chemical Properties Bases: Preparation of Bases and Alkalis, Test and Uses Physical and Chemical Properties of Acids, Preparation, Test and Uses of Acids. Acid: Definition, Basicity, and Types of Acid Families of elements in the periodic table Periodic table and Classification of ElementsAcademic Questions in Chemistry
With regards to redox reactions, which of the following statement is wrong?
A. Redox reaction are examples of chemical change
B. Reduction is the gain of electron
C. Substances that donates election during chemical reaction are termed reductants
D. Oxidizing agents are always reduced in chemical reactions
E. Oxidation occurs at the cathode in electrolysis
F. Hydrogen is a reducing agent
In chemistry, physical change is associated only with the rearrangement of molecules while the internal composition of the substance remains the same.
A. True
B. False
_____ electron(s) is a term that describes the number of electron(s) in the outermost shell of an atom.
A. Outer
B. Excess
C. Valence
D. Positive
E. Negative
F. Last
_____ is the negative electrode in electrolysis.
A. Anode
B. Anion
C. Cathode
D. Cation
E. Ion
F. Electrolyte
The above diagram shows the _____ type of bond.
A. Covalent
B. Polar covalent
C. Coordinate covalent
D. Metallic
E. Van dear walls
F. Ionic
Metals are referred to as _____ in their impure state.
A. Diluted
B. Consecrated
C. Coloured
D. Ores
E. Stained
F. Strained
Metals generally have the quality to shine, glow, sparkle, glitter, reflect light and be polished. This characteristic of metals is termed _____.
A. State
B. Ductility
C. Luster
D. Malleability
E. Hardness
F. Inflorescence
The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.
A. Mole
B. Volume
C. Weight
D. Number of moles
E. Mass
F. Amount of substance
The separation of mixtures can be carried out via the appropriate separation technique.
As discussed in a previous article, mixtures are composed of two or more substances physically combined.
In this article, we will continue with the various separation techniques. Meanwhile, it is recommended you read the commencement of this topic here.
Below are other methods through which mixtures are separated.
Fractional distillation is a method used for separating mixtures that contains more than two miscible liquid with a close range of boiling points.
A typical example of a mixture separated via fractional distillation is petroleum or crude oil.
If the difference in boiling point is greater than 250C, a simple distillation should be used.
Crude oil contain various fractions and these can be separated via fractional distillation.
The fractions of crude oil (petroleum) are listed below from the most volatile to the least volatile.
For now, think of a volatile substance as one that has a lesser boiling point and is easily evaporated at normal temperatures.
The fractions of petroleum are:
Fuel gas (most volatile)
LPG
Refinery gas
Gasoline
Petrol
Naphtha
Paraffin
Kerosene
Diesel oil
Gas oil
Fuel oil
Lubricating oils
Wax
Bitumen (least volatile)
The image below shows the process of fractional distillation as seen in an industrial environment.
Seen in the image are:
Notice that the gases at the top of the fractionating column have lower boiling points. They are the most volatile while bitumen asphalt (at the bottom) is the least volatile.
The image below shows the process of fractional distillation as seen in a laboratory:
An important apparatus that makes fractional distillation possible is the fractionating column.
The fractionating column functions to separate the mixture (crude oil in our instance) into its fractions or constituents based on the differences in their boiling point and volatilities.
Note: The fractionating column is absent in simple distillation.
You can read on simple distillation here.
Processes of fractional distillation
Precipitation is a method used to separate ions in aqueous solution. In this instance, a solution is considered to be aqueous if it contains water as its solvent.
As an instance, if two ions are present in an aqueous solution; let’s say copper ions (Cu2+) and silver ions Ag+); one of the ions can be precipitated out of solution if we added another solvent like hydrochloric acid or HCl into the aqueous solution.
The precipitated substance or solid (or ion in the above instance) is termed a precipitate.
Meanwhile, understand that the term precipitation means to bring about the deposition of a substance in its solid form from a solution.
With reference to our initial instance, on addition of HCl into the aqueous solution, silver ions (Ag+) will be precipitated out as silver chloride (AgCl) while the copper ions (Cu2+) still remain in the aqueous solution.
Below is the equation for the reaction:
Ag+(aq) + Cu2+(aq) + Cl-(aq) -> AgCl(s) + Cu2+(aq)
Please read the introduction to electrolysis and ions here.
The diagram below shows the precipitation of lead ions (Pb2+) and iodide ions (I-) as lead iodide (PbI2) in the reaction between lead trioxonitrate(V) - Pb(NO3)2 and sodium iodide (NaI2).
The process of precipitation can also be applied in the purification of impure compounds.
Other techniques utilized in the separation of mixtures are:
Magnetization or magnetic separation is used to separate solids that are attracted to magnets from those that aren't.
A mixture of iron filings and sulphur can be separated via magnetization.
The above statement is valid because the iron filings will become attracted to a magnet while sulphur particles remains unattracted inside the container.
Please read on the physical properties of metals here.
Crystallization is a separation technique used for separating two salts with different solubilities. In this regard, the less soluble salt is crystallized out of solution.
Please read on salts chemistry here.
Crystallization is also applied in the purification of soluble salts that contains insoluble solid impurities.
It is used to separate components of a complex mixture in solution, for instance ink.
Below are some types of chromatography:
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Amazing facts in Chemistry
Plastic and Glass can decompose, but not in our lifetimes. It takes an average time of 450 years for plastics to decompose. As for the decomposition of glasses, it takes about 4,000 years
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals.
Copper is the only metal that is naturally antibacterial. For this reason, some children utilize 'copper water bottles' in schools
Water freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
Notable points in Chemistry
Below are the physical properties of metals:
They exist in solid state.
The have high densities.
They are good conductors of heat and electricity.
The have the ability to be polished, to glow, sparkle and reflect light.
They can be bent, flattened and made into sheets called foils.
They can be drawn into wires.
Iron undergoes magnetism while most metals are poorly magnetized.
They typical have high melting point.
They generally have high boiling point.
With the exception of lithium, sodium and potassium, most metals are generally hard.
They have the ability to make sound when in contact with other objects or metals.
Please read details on the physical properties of metals here
John Dalton is an English chemist who brought clarity into the composition of matter and the basis for their chemical reactions.
Below are Dalton's Atomic Theory:
All matter consists of tiny indivisible particles called atoms.
Atoms of the same element are identical to each other in every aspect because they have the same shape and mass, while atoms of different elements are different in all respect.
Atoms are indestructible and can neither be created nor destroyed.
Atoms of different elements can combine with each other in simple whole number ratios to form compounds.
Atoms of the same element share similar physical and chemical properties. They can also combine in more than one ratio to form two or more compounds.
Meanwhile, understand that the above theories of John Dalton had been modified.
Please read on Dalton's atomic theory and its modifications here
The periodic table, also called periodic table of elements or Mendeleev's table, is a table that shows an organized arrangement of the 118 chemical elements according to their atomic number.
Out of the 118 elements; elements 1 - 94 are present in nature while elements 95 - 118 are synthesized artificially.
The manner at which elements are arranged on this table reveals some similarities in their electronic configurations and chemical properties.
A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)
Step 1: Identify the given parameter from the question.
Fe = 69.94%, O = 30.06%.
Empirical formula = Fe?O?
Step 2: Convert the percentages to gram. (just attribute grams to the %).
Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in emperical formula.
Mole of Fe: 69.94/55.85 = 1.252mol
Mole of O: 30.06/16 = 1.879mol
Step 4: Divide both sides by the smallest mole ratio.
Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1, 1.879/1.252 = 1.5
We now have the formula = Fe1O1.5
Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.
For iron (Fe), we will have 1 x 2 = 2
For oxygen (O), we will have 1.5 x 2 = 3
Step 6: Write the empirical formula.
The empirical formula= Fe2O3
Iron(III)tetraoxosulphate(VI)
In chemistry, hydrocarbons can be classified as either aliphatic or aromatic. Recently, both classifications of hydrocarbon were based on their structure rather than their origin.
Aliphatic hydrocarbons are put into three main groups according to the types of bonds they possess. These are:
Alkanes
Alkenes
Alkynes
They are shown in the image below:
It's important to note the followings:
Alkanes have single bonds (only) in their structures.
Alkenes always have a carbon-carbon double bond present in their structure.
Alkynes always have a carbon-carbon triple bond present in their structure.
Aromatic hydrocarbons are classified into:
