Alfred Ajibola
- Wed, 10th July, 2019 @ 4:52 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
At one point or another, we must have used a common salt in cooking our food. This 'cooking salt' or better still, table salt or common salt as it is often called is just one of the numerous salts we have in chemistry.
Chemically, this table salt (or common salt) is referred to as sodium chloride with a chemical formula - NaCl.
NaCl is naturally present in the oceans and seas which makes up the salt water habitat. This habitat serves as a home to a variety of organisms.
You can read on elements, compounds and mixtures here.
Generally, a salt can be defined as a compound or substance composed of a positive metallic ion and a negative non metallic ion.
As an instance, Na ion (Na+) is a positive metallic ion while chlorine ion (Cl-) is a negative non metallic ion. NaCl is therefore a salt based on our definition.
Please read more on ions here.
In the laboratory, salts can be prepared in a variety of ways. As a result, salts are of different types. In this regard, the ideal definition of a salt will be based on how the salt was formed. This implies that we will have different definition for salts based on how they were formed.
Below are various types of salt alongside their explanations:
A normal salt is formed from an acid and a base. Based on its formation, a normal salt is a product formed when an acid reacts with a base.
The acid and the base must be of equal strength. For instance, a strong acid is reacted with a strong base in the formation of a normal salt.
This reaction involving an acid and a base is termed 'neutralization reaction'. The other product formed from a neutralization reaction is water (H2O).
Recall that an acid will always have an hydrogen ion as its only positive ion. To this end, a normal salt is formed only when all the hydrogen ions have been replaced by the metallic ion from the base.
Please read more on acids here.
Meanwhile, recall that a base will always have hydroxide ion (OH-) as its only negative ion.
The equation below shows the formation of a normal salt.
HCl + NaOH -> NaCl + H2O
Acid Base Salt Water
Notice that the hydrogen ion (
A normal salt is electrically neutral since the number of hydrogen ions (H+) from the acid reacts with the exact number of hydroxide ions (OH-) from the base.
It is also important to add that normal salts can be formed when:
Metal reacts with an Acid: Hydrogen gas is given off during this process. Consider the equation below:
Mg(s) + 2HNO3(aq) -> Mg(NO3)2(s) + H2(g)
Mg(NO3)2 is the salt formed from the above reaction. This salt qualifies as a normal salt.
Acid reacts with Carbonates: Carbon(IV)oxide (CO2) and water (H2O) are always given off during this reaction. The equation is shown below:
2HCl(aq) + Na2CO3(s) -> 2NaCl(s) + H2O(l) + CO2(g)
In the formation of an acid salt, only a part of the hydrogen ions in the acid is replaced. As a result, hydrogen ion is always present in acid salts. In fact, it is the presence of hydrogen ion (H+) in the salt that makes it an acid salt.
Meanwhile, always understand that the acid required to form an acid salt must have a basicity greater than one.
The basicity of an acid is the number of replaceable hydrogen ion(s) in one molecule of the acid.
As an instance, hydrochloric acid (HCl) is monobasic since it has only one replaceable hydrogen ion within it.
Hydrogen tetraoxosulphate(VI) acid (H2SO4) is dibasic since it has two replaceable hydrogen ions within its molecule.
From the above instance, it is quite clear that HCl cannot form an acidic salt since it is monobasic.
Conversely, H2SO4 will form an acid salt because it is dibasic: that is, it contains 2 replaceable hydrogen ions in one molecule of the acid.
The equation below shows the formation of an acid salt:
H2SO4(aq) + NaOH(aq) -> NaHSO4(s) + H2O(l)
From the above equation, understand that one of the hydrogen ions from the acid (H2SO4) had been replaced by sodium (Na).
You can read on physical and chemical changes here.
Unlike an acid salt which contains hydrogen ion (H+), a basic salt contains hydroxide ion (OH-) within it.
A basic salt will always contain the positive metal ion from the base, hydroxide ion from the base and the negative ion from the acid.
When a strong base reacts with a weak acid, a basic salt is formed. Also, when the concentration of a base is much higher than the acid, a basic salt will also be formed.
Examples of basic salts are ZnOHCl and MgOHCl
A double salt is one that ionizes to produce three different types of ions is solution. From the ions formed, two are positively charged while one is negatively charged.
Examples of double salts are:
Notice that if KAl(SO4)2.12H2O was dissolved in water, the ions produced will include:
Potassium ion (K+) which is positively charged.
Sulphate ion (SO42-) which is negatively charged.
Similarly, (NH4)2 Fe(SO4)2.6H2 will ionize to produce:
Positively charged ammonium ion (NH4+)
Positively charged iron (II) ion (Fe2+)
Negatively charged sulphate ion (SO42-)
Any salt that contains complex ions within it is regarded as a complex salt. In simple terms, consider complex ions to always consist of a charged group of atoms.
An example of a complex salt is sodium tetrahydroxozincate(II) or Na2Zn(OH)4. If this complex salt is dissolved in water, sodium ions (Na+) and Zinc hydroxide ions - Zn(OH)2- will be produced respectively. It is the presence of Zn(OH)2- (which is a complex ion) that makes this salt a complex salt.
Another example of a complex salt is potassium hexacyanoferrate(II) or K4Fe(CN)6 which ionizes to produce potassium ion (K+) and [Fe(CN)6]4- respectively. It is the presence of [Fe(CN)6]4- (a complex ion) that makes K4Fe(CN)6 a complex salt.
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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:
