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 rate of a chemical reaction refers to how quickly reactants are converted into products over a specific period of time. In this regard, the rate of chemical reaction is often determined (experimentally) by measuring the change in concentration of one of the components (that is: change in reactants, or change in product) in the reaction with time.
The rate of chemical reaction is a fundamental concept in chemistry, critical for anyone curious about the science of reactions in our everyday lives. Whether in the kitchen or a laboratory, understanding how and why reactions occur at different rates empowers us to apply this knowledge to improve our lives and the world around us.
The rate of chemical reaction is defined as the number of moles of reactants converted or moles of products formed per unit time.
You can read on the postulate of the kinetic theory of gases here.
The rate of a reaction can be measured in different ways, typically by focusing on changes in concentrations of the reactants, or products over a period of time.
One method is to observe how quickly reactants disappear, or how quickly products appear. For example, the disappearance of color in a reaction can indicate the rate of the process.
Another approach is monitoring gas production, such as measuring changes in volume over time in a closed system. As stated ealier, concentration of reactants or products is one of the properties of a reaction that can change with time.
You.can read on Le Chatelier's principle in chemistry here.
Below are properties of a reaction system that can change with time; and thus can be used to measure reaction rate.
A change in the concentration of reactants or products.
The decrease in the mass of the reaction system.
Change in the total gas pressure of the system.
The volume of gaseous product produced.
Amount of precipitate formed.
Change in colour intensity.
Change in pH.
When a reaction proceeds, the concentration of reactant(s) start decreasing while the concentration of product(s) start increasing. Therefore, the rate of chemical reaction can also be expressed thus:
Rate of chemical reaction = Decrease in concentration of a reactant / Time interval
Rate of chemical reaction = Increase in concentration of a product / Time interval
Average rate of reaction = Change in Quantity / Change in Time
Please read on gas laws in chemistry here.
Note: In a rate of chemical reaction, the concentration of reactants or products is measured in mol/dm3. The time taken to calculate changes in the reaction is measured in seconds. Therefore, the unit of the rate of reaction is mol/dm3/s (or g/dm3s-1).
Understand that the rate of reaction can also be measured by the change in the number of mole ((or mass) of reactants or products divided by the time taken for the change. Therefore, the rate of chemical reaction may also be expressed below:
In the above formula, its unit becomes mol/s (mols-1) or g/s (gs-1).
Please read solved calculations on Boyle's law here.
The rate of chemical reaction can be graphically expressed via the rate curve.
The rate curve is a graphical represention of the rate of chemical reaction. It is shown below:
A rate curve shows the following features (or characteristics):
It always commences through the origin. This is true because there isn't any change in the molar (or mass) concentration of the reactants at the start of the reaction.
The rate curve is always steep when the reaction proceeds. This is so because the reaction rate is fastest at the beginning.
The rate curve becomes less steep. This is true since the reactants are used up during the course of the reaction.
The curve turns horizontally at the end of the reaction. This is so because all the reactants had been used up; thus bringing the reaction to its completion.
You can read on Avogadro's number explained with worked examples here.
From the rate curve, we can determine the average rate of a reaction through the formula below:
Average rate curve = Total number of mole (or mass) involved in the reaction ÷ by the time taken.
We can also calculate the rate at a particular instance of the reaction. This is equivalent to the gradient at a point on the curve.
You can attempt academic questions and answers in chemistry here.
Below is a JAMB question on rate curve:
The following graph demonstrates the rate of reaction between calcium carbonate (marble) and dilute hydrochloric acid. The graph shows that the rate of reaction is initially greatest when:
A. The initial slope of the curve is steepest and this occur when small pieces of marble are used and is due to a small surface area of reactant.
B. The initial slope of the curve is steepest and this occur when large pieces of marble are used due to a small surface area of reactant.
C. The initial slope of the curve is steepest and this occurs when small pieces of marble are used and is due to a large surface area of reactant.
D. The initial slope of the curve is steepest and this occur when large pieces of marble are used as a result of large surface area of reactant.
E. The initial slope of the curve is least steep and this occur when small pieces of marble are used and is due to the increased surface area of the reactant.
Correct Answer: C
The answer is a function of the "surface area of reactants;" which happens to be one of the factors that can affect reaction rate. In this regard, notice that the rate of reaction was faster when small pieces of marble was used (as seen in the second rate curve). This small pieces of marble presents a larger surface area, thus resulting into more effective collisions.
The surface area of reactants, alongside other factors that affect rate of chemical reaction are explained via the link below.
Please read on the factors that affect the rate of chemical reaction here.
Importantly,, before a chemical reaction can proceed, there has to be a series of collision between the reactant particles. This collision resulting from the kinetic energy of the reactant particles may overcome an energy barrier termed activation energy; thus leading to a successful chemical reaction. Simply put, collisions leading to chemical reaction are termed effective collision, and the energy of reactant particles must be equal or greater than the reaction's energy barrier (termed "activation energy" or Ea).
An understanding on collision theory and activation energy is crucial towards understanding why chemical reaction occur, and consequently, the rate of chemical reaction.
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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:
