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
The ionic theory is an important concept associated with electrolytes and electrolysis. This is so because electrolytes will always dissociate into ions during electrolysis.
An electrolyte is defined as a solution or molten compound or paste-like compound that conducts electricity. Electrolytes are able to conduct electricity because they dissociates into two types of ions. These are: cations and anions.
An understanding on electrolytes and ions is required towards comprehending ionic theory and electrolysis.
The equation below will be used to explain the ionic theory:
YZ -> A+ + B-
KCl -> K+ + Cl-
Ideally, the electrolyte (YZ or KCl) from the above instance should be in an aqueous form. In short, all electrolytes exists in aqueous (solution), or molten or paste-like forms. (Please see the definition of an electrolyte above).
The above equation can therefore be appropriately re-written as:
Y+Z-(aq) -> Y+(aq) + Z-(aq)
K+Cl-(aq) -> K+(aq) + Cl-(aq)
The process whereby molecules are splitted into ions in an electrolyte is termed ionization or dissociation.
All electrolytes do not ionize to the same degree. This is so because electrolytes fall into 2 categories. These are:
From the above explanations, the ionic theory of electrolysis can therefore be related or linked to the ionization (or dissociation) of ions in solution.
The ionic theory of electrolysis states that substances whose solution conducts electricity will undergo electrolytic dissolution, dissociation or ionization.
The ionic theory of electrolysis was first proposed by a Swedish scientist named Svante Arrhenius in 1887.
You can read on the physical and chemical properties of acids here.
Electrolysis is defined as the process of passing electricity into an electrolyte through the electrodes, with the resultant decomposition of the electrolyte.
In the above definition, the 'decomposition of electrolyte' implies that the electrolyte is eventually broken down into its constituent elements.
Please read on elements and their characteristics here.
The elements deposited or liberated during electrolysis will vary in different ionic compounds. For instance, the elements deposited at the electrodes in the electrolysis of fused calcium chloride (CaCl2) will be different from that deposited in the electrolysis water (H2O).
Please read on physical and chemical changes in chemistry here.
Electrodes are defined as rods or plates that connect an electric circuit to the electrolyte; thus becoming the avenues through which electric current enters and leaves the electrolyte.
The diagram below shows the various components of electrolysis:
Notice from the above diagram that the electrodes (cathode and anode) are in contact with the electrical circuit at one end and with the electrolyte at the other end.
Please read on the physical properties of metals here.
Electrodes are of two types. They are:
1. Anode: The anode is the positive electrode through which electric current (or electrons) leaves the electrolyte.
The anode will attract negatively charged ions (called anions) during electrolysis (or when current is passed through the electrolyte).
2. Cathode: This is the negative electrode through which electric current (electrons) enters the electrolyte.
The cathode will attract positively charged ions (cations) during electrolysis.
During electrolysis, oxidation occurs at the a anode while reduction occurs at the cathode.
Oxidation is defined as the loss of electron(s) in a chemical reaction.
Reduction is the gain of electron(s) in a chemical reaction.
An understanding of the terms (explained above) is crucial towards comprehending the electrolysis of different compounds.
The exact way and manner through which oxidation and reduction occur in electrolysis will be clearly explained in a subsequent article on the electrolysis of various compounds.
At the moment, You can read on the definitions of acid in regards to oxidation and reduction 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:
