Alfred Ajibola
- Mon, 20th January, 2020 @ 1:20 PM
Topics in Chemistry
Gas laws in chemistry Charles's law explained Calculation questions on Charles's law Examples of Charles's law in real life Boyle's law explained Calculation questions on Boyle's law Examples of Boyle's law in real life Summary on the kinetic molecular theory of gases Postulates of kinetic theory of gases Avogadro's number explained with worked examples Mole and Avogadro's Number explained Le 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 What are mixtures? Characteristics of mixturesAcademic 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
All forms of matter, whether visible or invisible to the human eyes, will always have their unique physical and chemical properties.
Please read on the concept of matter here.
Chemical properties of matter are those features or characteristics of matter that describes the ability of matter to form new substances through chemical reactions.
You can read on the physical properties of matter here.
The term chemical property is ascribed to matter whenever it undergoes a change to form an entirely new substance. Such change is termed a chemical change.
Please read on the differences between physical and chemical change here.
Having a good understanding of 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.
You can read on the concept of physical and chemical change here.
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. The oxidation of iron refers to its reaction with oxygen and water to form rust. This process is called corrosion.
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.
Please read on the physical and chemical properties of acids here.
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) in a chemical reaction. Both processes (oxidation and reduction) occurs simultaneously in a reaction; and such reactions are termed redox reactions.
For instance, in the formation of rust, iron (Fe) is oxidized into rust because it loses its electrons to another element (oxygen and 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.
Please read more on the concepts of ions and electrolytes here.
The substance that donates electron(s) during a chemical reaction are termed reducing agents, reductant or reducer while that which accept electron(s) are termed oxidizing agents, oxidant or oxidizer.
In redox reactions, the oxidizing agents are always reduced while the reducing agents are simultaneously 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 and chemical properties.
Please read more on the concept and definitions of acid here.
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.
Please read on gaseous state of matter and their characteristics here.
It is noteworthy to state that whatever undergoes burning will change into a new substance; and that's a chemical change.
You can read on elements and their characteristics here.
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 reactants) are converted to one or more substances called the products through the rearrangement of their molecular or ionic structures.
You can read on molecular mass and relative molecular mass here.
A chemical reaction brings about the rearrangement of the constituent atoms of the reactants in order to create products with a different atomic structures.
Please read more on Dalton's atomic theory and its modifications here.
When substances undergo burning, heat is realeased. This makes heat an observable feature during burning.
You can read on the concepts of heat and temperature here.The heat of combustion is defined as the amount of heat released when a specific mass or volume of a substance is burned completely.
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 since a new thing is always 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 a substance from its constituent elements at standard temperature (298K) and pressure (1 atm).
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. Examples are wood, plastic and rubber. In addition, fuels like korosene, petrol and methane (cooking gas) are all considered to be highly flammable.
Please read more on the introduction to hydrocarbons here.
'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).
Please read on the characteristics of living organisms here.
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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:
