• NUCLEAR CHEMISTRY (I)
• NUCLEAR CHEMISTRY (II)
• SIMPLE MOLECULES AND THEIR SHAPES
• PETROLEUM OR CRUDE OIL
• VOLUMETRIC (QUANTITATIVE) ANALYSIS
• QUALITATIVE ANALYSIS

Nuclear Chemistry (I)

Chemistry SS3 Second Term

Week 1

Topic: Nuclear Chemistry

Nuclear Reactions

Rutherford in 1919 transmitted nitrogen isotope into an oxygen isotope. The nitrogen was subjected to the action of swift alpha – particles derived from radium salt.

Transmutation is the process by which radioactive elements change into different elements.

Nuclear reaction is a process in which two nuclei or nuclear particles collide, to produce different products than the initial particles.

Nuclear fission and nuclear fusion both are nuclear phenomena that release large amounts of energy, but they are different processes which yield different products. Learn what nuclear fission and nuclear fusion are and how you can tell them apart.

Nuclear Fission

Nuclear fission takes place when an atom’s nucleus splits into two or more smaller nuclei. These smaller nuclei are called fission products. Particles (e.g., neutrons, photons, alpha particles) usually are released, too. This is an exothermic process releasing kinetic energy of the fission products and energy in the form of gamma radiation. Fission may be considered a form of element transmutation since changing the number of protons of an element essentially changes the element from one into another.

Nuclear Fission Example:

²³⁵₉₂U + ¹₀n → ⁹⁰₃₈Sr + ¹⁴³₅₄Xe + 3¹₀n

Nuclear Fusion

Nuclear fusion is a process in which atomic nuclei are fused together to form heavier nuclei. Extremely high temperatures (on the order of 1.5 x 10⁷°C) can force nuclei together. Large amounts of energy are released when fusion occurs.

Nuclear Fusion Examples

The reactions which take place in the sun provide an example of nuclear fusion:

¹₁H + ²₁H → ³₂He

³₂He + ³₂He → ⁴₂He + 2¹₁H

¹₁H + ¹₁H → ²₁H + ⁰₊₁β

Comparison between Nuclear Fission and Fusion

	Nuclear Fission	Nuclear Fusion
Definition:	Fission is the splitting of a large atom into two or more smaller ones.	Fusion is the fusing of two or more lighter atoms into a larger one.
Natural occurrence of the process:	Fission reaction does not normally occur in nature.	Fusion occurs in stars, such as the sun.
Byproducts of the reaction:	Fission produces many highly radioactive particles.	Few radioactive particles are produced by fusion reaction, but if a fission “trigger” is used, radioactive particles will result from that.
Conditions:	of the substance and high-speed neutrons are required.	High density, high temperature environment is required.
Energy Requirement:	Takes little energy to split two atoms in a fission reaction.	Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.
Energy Released:	The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion.	The energy released by fusion is three to four times greater than the energy released by fission.
Nuclear weapon:	One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.	One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to “trigger” a fusion reaction.

Comparison of Nuclear Reaction and Ordinary Chemical Reaction

Nuclear Reaction	Ordinary Chemical Reaction
During nuclear reactions, the nuclei of atoms undergo change and therefore new elements are formed as a result of such reactions.	During chemical reactions, elements do not lose their identity. In these reactions, only the electrons in the outermost shell of atoms participate whereas the nuclei of atoms remain unchanged.
Reactivity of an element towards nuclear reactions is nearly independent of oxidation state of the element. For example, Ra element or Ra2+ ion in RaC2 behave s similarly during nuclear reactions.	Reactivity of an element towards chemical reactions depends upon the oxidation state of the element. In ordinary chemical reactions, Ra and Ra2+ behave quite differently.
In nuclear reactions, isotopes behave quite differently. For example, U-235 undergoes fission quietly readily but U-238 does not.	Different isotopes of an element have nearly same chemical reactivity.
Rate of a nuclear reaction is independent of temperature and pressure.	Rate of a chemical reaction is largely affected by temperature and pressure.
A nuclear reaction cannot be reversed.	A chemical reaction can be reversed.
Nuclear reactions are accompanied by large energy changes.	Chemical reactions are accompanied by relatively small energy changes.

Assessment

What is the most significant difference between Nuclear fission and fusion?

What does Transmutation mean?

Petroleum or Crude Oil

Chemistry SS3 Second Term

Week 4

Topic: Petroleum or Crude Oil

Crude Oil

Crude oil or Petroleum is the chief source of hydrocarbons. Petroleum which means rock oil in Latin occurs as a dark, sticky, viscous liquid. It is found in huge underground deposits in many parts of the world. Natural gas is usually found together with it. Petroleum is a mixture of gaseous liquid and solid alkanes, alkenes, cycloalkanes, aromatic hydrocarbons and others. Natural gas consists mainly of methane.  Crude oil is a mixture of hydrocarbons. It exists in liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface separating facilities.

Crude oil occurs in large quantities in Nigeria, especially in Bayelsa, Edo, Imo, rivers, Delta, Abia, Ondo and Cross river state. It is dark brown in colour though its composition and consistency vary from place to place. In fact, different oil producing areas yield significantly different varieties of crude oil. We have light and heavy crude oil. The light one has low metal and sulphur content, light in colour and flows easily. It is very expensive. The heavy one has high metal and sulphur content and must be heated to become fluid. It is less expensivePetroleum  is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth’s surface, which is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation.

It consists of hydrocarbons of various molecular weights and other organic compounds

Origin of Crude Oil and Natural Gas

They are formed from the remains of marine algae and animals. When these tiny aquatic organisms died, their remains gradually settled on the seabeds. Over the years, the remains became covered by mud, silt and other sediments. As the sediments piled up, their mass exerted a great pressure on the lower layers, changing them to hard sedimentary rocks. During this process, bacterial activity, heat and pressure probably changed the plant and animal remains into crude oil and natural gas. 

Refining of Crude Oil

Petroleum or crude oil occurs naturally. it contains many useful products also called fractions. These are separated by the method of fractional distillation. This process of obtaining useful fractions from petroleum is called refining. 

The process of dividing petroleum into fractions with different boiling range volatilities and free from impurities is called refining.
The process of turning petroleum into a useful form is done in a crude oil refinery. The steps for making crude oil into oil, petrol or whatsoever are fractional distillation, cracking and reforming.

Petroleum is refined by fractional distillation. The process of separating a mixture into a series of fractions of different volatilities by means of distillation is known as fractional distillation.
In the process of fractional distillation, a mixture of different liquids is evaporated followed by condensation. Different liquids are evaporated according to their boiling point and they are collected in different chambers of distillation tower

Fractional Distillation of Crude Oil

Fractional distillation differs from distillation only in that it separates a mixture into a number of different parts, called fractions. A tall column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with low boiling points condense at the top. Like distillation, fractional distillation works because the different substances in the mixture have different boiling points.

Fractions of petroleum from refining are petroleum gases (Methane, butane, etc.), petrol or gasoline, kerosene, diesel, lubricating oil and bitumen (asphalt). Because they have different boiling points, the substances in crude oil can be separated using fractional distillation. The crude oil is evaporated and its vapours allowed to condense at different temperatures in the fractionating column. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms. 

The mixture is inserted at the bottom, where mostly everything will condense as the temperature is 350°C and more. The condensed crude oil will rise to the next fraction above, which has a very high temperature as well, but a slightly smaller one. Only the part of the mixture, which boiling point is under the temperature of the fraction, will condense and rise to the next fraction. The part of the mixture, whose boiling point is higher than the temperature inside the distillation fraction, will stay there and be pumped out.

Crude oil is heated until it boils and then the hydrocarbon gases are entered into the bottom of the fractionating column. As the gases go up the column the temperature decreases.
The hydrocarbon gases condense back into liquids and the fractions are removed from the sides of the column. The different fractions have different uses.The smaller the hydrocarbon molecule, the further it rises up the column before condensing.
The fractionating column operates continuously. The temperatures shown are approximate. A sample of crude oil may be separated in the laboratory by fractional distillation. The collection vessel is changed as the temperature rises to collect the different fractions.

Cracking

After the fractional distillation process, the separated mixtures have to be cracked down. This means that a long molecule will be split up in smaller parts.
Firstly, single bonds will be broken down. This results into some lone electrons.
The lone electrons form double bonds. Thus, hydrogen will disconnect from the carbon atom. Hydrogen (H₂) remains as a side product. The loss of hydrogen in these smaller organic molecules is logical, because when they are lost, more lone electrons remain with what the previous lone electrons can make a bond.

Reforming

After cracking, the molecules are ready to undergo the reforming process.
This is given by the octane number. The octane number is very important in petrol. It tells what the percentage of pure heptane (in the earlier days it was octane – that is why it is called octane number) in petrol is. This is of great importance for the chemical behaviour. The quality of petrol is improved by adding mixtures to pure heptane. The chains of heptane are heated up (where platinum is used as a catalyst). So they can change. After the heating process, it shows a higher amount of branched chains. This increases the octane number.

Example: When the petrol you buy has a 98 in the name, then it means that 98% are branched chains and 2% of the mixture is pure heptane (or another pure molecule).

Octane Number

The octane number or octane rating of petrol is a measure of the proportion of branched chain hydrocarbons in a given blend of gasoline (petrol).

In other words, Octane number is a standard which determines the knocking ability and quality of gasoline. Higher is the octane number of a gasoline, lower is the knocking it produces.

Gasoline is composed of C7 – C9 hydrocarbons i.e. heptanes, octane and nonane. These hydrocarbons are present in their straight chain or branched chain isomers. It has been shown that straight chain hydrocarbons burn too rapidly in the car engine thus, causing irregular motion of the pistons which results in rattling noise. This rattling noise is known as “Knocking”.

Knocking

Knocking is a sharp metallic sound produced in the internal combustion engine. Knocking is caused by the low octane number of gasoline

Synthetic Petrol

Synthetic petrol is made from materials such as coal, coke and hydrogen which do not occur in crude petroleum. Synthetic petrol can be gotten from two sources

1. From coal: When powdered coal is heated with hydrogen in the presence of iron or tin as catalyst at 500^oC and 200 atmospheric pressure, it is converted into an oily mixture of hydrocarbons. The mixture is separated by distillation into a petrol fraction boiling at 200^oC and a heavy oily residue which can be further treated with fresh coal to obtain more petrol
2. From Coke: When steam is passed over heated coke at 1000^oC, a mixture containing equal volumes of carbon (II) oxide and hydrogen known as water gas is obtained
   1. C_(s) + H₂O_(l) —–> CO_(g) + H_2(g)

The water gas can be hydrogenated to a mixture of hydrocarbons by adding hydrogen and passing it over finely divided nickel as catalyst at 200^oC. About half of the product is petrol, the less volatile fraction is used as fuel for diesel engines

Fractions of Crude Oil

1. Petroleum gases – These gases are liberated at the top of the column at temperatures below 40^o They are mainly hydrocarbons consisting of one of four carbon atoms per molecule, e.g methane, ethane, propane, butane and ethane. They are used mainly as fuels for homes and industries and for manufacture of products like hydrogen, sulphide and ethyne
2. Petroleum ethers and ligroin – This is the mixture of very volatile liquids consisting of hydrocarbons with five or seven carbon atoms per molecule. The petroleum ether or light petroleum distils over between 2^oC to 60^oC, while the ligroin or light naphtha distils over between 60^oC to 100^o
3. Petrol – Petrol or gasoline is a mixture of hydrocarbons consisting of four to twelve carbon atoms per molecule. It is a volatile liquid which distils over in the temperature range of 40^oC to 200^o Petrol is used as a fuel for aeroplanes and motor vehicles. It is a good solvent for paints and grease
4. Kerosene – Kerosene contains hydrocarbons with twelve to eighteen carbon atoms per molecule. It distils over in the temperature of 200^oC to 250^o it is a fairly volatile liquid and is used as a fuel for lighting and heating and for driving tractors and some modern jet engines. It is a good solvent for paint and grease
5. Gas oil and Diesel oil – They have twenty to twenty five carbon atoms per molecule. They distil over in the temperature of 250^oC to 350^o They are mainly used as fuel for heating and diesel engines and as raw materials of the cracking process
6. Lubricating oils – They are heavy oils. They consist of hydrocarbons with more than twenty five carbon atoms per molecule. They distil over in the temperature of 350^oC to 500^o They are viscous liquids used for lubricating moving parts of engines and machines. Grease belongs to this group. Vaseline and paraffin wax are solid long chain hydrocarbons which are obtained from re-distillation of heavy oils.
7. Bitumen and other residues – these are solid residues left behind at temperatures above 500^o Bitumen are used for surfacing roads and airfields while other residues may be used as fuel, in protective paints and water proofing roofs.

Assessment

1. ……… is the chief source of hydrocarbons
2. ………. of petrol is a measure of the proportion of branched chain hydrocarbons in a given blend of gasoline (petrol).
3. ……….. involves the separation of a mixture into a number of different parts, called fractions.
4. ……….. is a sharp metallic sound produced in the internal combustion engine
5. Mention 4 fractions of crude oil

Answers

1. Crude oil/Petroleum
2. Octane Number
3. Fractional Distillation
4. Knocking
5. Kerosene, Petrol, Bitumen, Diesel, Gas oil, Lubricating oil