Topics in ChemistryLe Chatelier's Principle: Changes in concentration and pressure in dynamic equilibrium Chemical Equilibrium: Dynamic Equilibrium in Chemistry Static and Dynamic Equilibrium explained with their Differences Chemistry Scheme of Work, SS1, First Term Chemistry Scheme of Work, SS1, Second Term Chemistry Scheme of Work, SS1, Third Term Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry
Academic Questions in Chemistry
Which of the following isn't an element of the periodic table.
According to the periodic table, elements in the same group have got the same number of shells.
The periodic table of elements is also called the Mendeleev's table.
The simplest formula of a compound is termed _____.
A. Emperical formula
B. Molecular formula
C. Avogadro's number
D. Mass formula
E. Molar mass formula
F. Mole ratio
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)
Which of the following statement is false concerning hydrocarbons?
A. Hydrocarbons can be aromatic
B. Hydrocarbons are made up of carbon and hydrogen only
C. Alkynes are aliphatic hydrocarbons
D. Alkenes have a carbon-carbon double bond in their structure
E. Benzene ring has a carbon-carbon triple bond in its structure
F. Hydrocarbons are the main constituents of petroleum and natural gas
The ability of carbon to form long chain of itself is called _____.
A. Carbon chain reaction
E. Organic chemistry
F. Carbon moleculation
Calculate the relative molecular mass of methane. (Carbon = 12.001, H = 1.00794).
A. 13.00894 amu
B. 11.00206 amu
C. 12.00794 amu
D. 14.001 amu
E. 15.001 amu
F. 16.033 amu
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All forms of matter (whether visible or invisible to the human eyes) will always have their unique physical and chemical properties.
Chemical properties of matter are those features or characteristics of matter that describes the ability of matter to form new substances through chemical reactions.
The term chemical property is ascribed to matter whenever it undergoes a change to form an entirely new substance. Such change is referred to as a chemical change.
Note: Understanding the chemical properties of matter is an important part of Chemistry. In fact Chemistry is defined as the study of matter and the changes they undergo.
Using iron as an instance, one of its chemical properties will be its ability to react with oxygen and water leading to the formation of rust. The point to remember here is:
Iron has a chemical property called oxidation; and oxidation of iron refers to it's reaction with oxygen and water to form rust.
It important to state that the rust formed from iron in the above instance is entirely different from iron. It is these differences in the chemical composition of substances that make up their specific chemical properties.
Below are some explanations on the chemical properties of matter:
Oxidation and Reduction are important concepts in chemical reactions.
In simple words, Oxidation is the loss of electron(s) while Reduction is the gain of electron(s). Both processes (oxidation and reduction) occurs simultaneously in a reaction; and such reactions are termed as Redox reactions.
For instance, in the formation of rust, iron (Fe) is oxidized into rust because it loses it's electrons to another element (oxygen & water in this case). At the same time, water is reduced during this reaction because it gained electrons from iron. This is a redox reaction and it's summarized in the equation below:
Iron + Oxygen (from the atmosphere) dissolved in Water -> Iron Oxide (Rust)
4Fe(s) + 6H2O(l) -> 2Fe2O3 + 6H2
Iron (III) Oxide is the IUPAC name for Fe2O3 (rust) because its oxidation number had increased from +2 to +3 after it gave out (or donated) electrons to water molecules containing oxygen.
Note: The substance that donates electron(s) during a chemical reaction are termed reducing agents or reductant or reducer while that while that that accept electron(s) are termed oxidizing agents, or oxidant or oxidizer.
In redox reactions, the oxidizing agents are always reduced while the reducing agents are always oxidized. Iron, the reducing agent in the above instance was oxidized to rust.
Acidity is the level of acid in a substance.
Acids can be defined in a variety of ways. They also have their specific physical properties and chemical properties.
Burning is often referred to as combustion, although they aren't exactly the same thing. For instance, burning will always be accompanied with flames why combustion has no flame in its reaction.
Burning refers to an exothermic reaction (one that gives out heat) between a reducing agent (acting as fuel) and an oxidizing agent (typically oxygen). Flames are always seen during burning.
Without oxygen, burning will not occur. Similarly, without the substance to be burnt (fuel), burning will also not occur).
During burning, the reducing agent (fuel) is oxidized into a gaseous-like mixture referred to as smoke.
Note: Whatever undergoes burning will change into a new substance; and that's a chemical change.
Chemical reaction is the basis of the changes we see around us. In short, Chemistry is the study of matter and the changes they undergo.
A chemical reaction is said to occur when one or more substances (referred to as the reactants) are converted to one or more substances called the products through the rearrangement of their molecular or ionic structures.
A chemical reaction brings about the rearrangement of the constituent atoms of the reactants in order to create a product with a different atomic structure.
When substances undergo burning, heat is realeased. This makes heat an observable feature of burning.You can read on the Concepts of Heat and Temperature here.
The heat of combustion is simply defined as the amount of heat released when a specific mass or volume of a substance is burned completely.
Note: The value dervived from heat of combustion is always negative. This is so because reactions that releases the heat of combustion are exothermic.
The enthalpy of formation is also referred to as the heat of formation. A chemical change is always associated with the heat of formation because a new thing is formed after a chemical reaction had taken place.
The enthalpy of formation is defined as the change in heat released or absorbed during the the formation of one mole of the substance from its constituent elements at standard temperature (298K) and pressure (1 atm).
Note: The Standard International (SI) unit for enthalpy (or heat) of formation is KJ/mol.
The flammability of a substance is a chemical property of matter and it refers to the ability of a substance to catch and sustain fire.
Substances made up of carbon are always flammable, for example, wood, plastic and rubber. In addition, fuels like korosene, petrol and methane (cooking gas) are considered to be highly flammable.
Flammability Test is a procedure used in determining the ease or difficulty at which a material or finished product will ignite (or burn) when placed in a close range to fire or heat.
This is the degree to which a substance can harm living organisms. Such substances are referred to as toxic. Example of toxic substances include Hydrogen Sulphide (H2S) and Carbon monoxide (CO).
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Amazing facts in Chemistry
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
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:
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:
Organic chemistry is the study of carbon and it's compounds.
Carbon is the focus of organic chemistry because it has a wide chemical diversity in the sense that it can combine with other carbon atoms to form a long chain of carbon molecule. This ability and process whereby carbon can form a long chain of itself is called catenation.
A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.
Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.
The large molecules (above) have no specific chemical formula throughout their volume.
Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the modifications of Dalton's atomic theory.
Calculate the Relative Molecular Mass of methane (CH4). (Carbon=12.001 and H=1.00794)
Molecular Mass = Atomic mass of carbon + Atomic mass of Hydrogen
Methane is composed of one atom of Carbon and 4 atoms of Hydrogen.
12.001 + (1.00794 x 4)
Molecular Mass of Methane = 16.033 amu
Calculate the Relative Molecular Mass of water (H2O). (Oxygen=15.9994 and Hydrogen=1.00794)
Molecular Mass = Atomic mass of Hydrogen + Atomic mass of Oxygen
Water contains 2 atoms of Hydrogen and 1 atom of oxygen.
(1.00794 x 2) + 15.9994
Molecular Mass of Water = 18.015 Da
Below are some facts about gold:
It is the only metal that has a gold (golden) color
Gold is present inside the earth crust in all the seven continents
Pure gold is soft and very stretchable (It can even be stretched into threads)
The Latin name of Gold is aurum which means 'shining dawn'. For this reason, its chemical symbol is 'Au'
Gold is a very good conductor of electricity. This is why it’s sometimes used in making USB and audio cables
Gold is non toxic and can be eaten with food. It is sometimes added to desserts in some expensive restaurants
The term Gold originated from an ancient English word 'geolu' which means yellow
24karat gold is the purest gold element