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Jamb Tutorial 2016 - Chemistry Class - Forum

Solutionz
Solutionz
Welcome to Solutionclass Jamb Tutorial Centre for
Chemistry class
Lecturers in charge - Promzyguru

OVER TO YOU NOW

Mr Solution
Mr Solution
Matter consists 3 states which are solid,liquid nd gaseous states.dea characteristics are br /> solid- definite shape nd volume
liquid- no definite shape bt definite volume
gas- no definite shape nd volume

so matter undergoes changes which are CHEMICAL nd PHYSICAL changes.
Physical change- it is easily reversible nd no new substance is formed.example changing of ice to water nd to steam nd steam can also be changed back to water by cooling nd by cooling water can also be changed to ice, so u can see dat dey can be reversed nd no new substances are formed
other examples are br /> -sublimation of solids to vapour
- separation of mixtures by evaporation distillation etc.
-magnetization nd demagnetization of iron rods.
CHEMICAL CHANGE: dis is not easily reversible nd new substance is formed.just like wen a wood is burning it will gradually become ash which cannot be reversed to wood again .other examples are br /> -dissolution of metals nd limestone in acids
- rusting of iron
-slaking of lime
-fermentation nd decay of substance
-changes in an electrochemical cell

Matter can further be classified into ELEMENTS,COMPOUND nd MIXTURE
Element: it is a substance which cannot be broken down into simpler units by an ordinary chemical process.there are about 109 known elements which we shall discuss in details when we talk about periodic table. Elements are grouped as metals, semi metals or metalloids nd non metals

compound:it contains two or more elements chemically combined together.it is a chemical change.it has different properties from its constituent elements.it is also present in fixed ratio nd dat is why it is represented by a formula example water is represented with H2O,sand(silicon nd oxygen) SiO2,limestone CaCO3 etc.

Mixtures:contains two or more constituents which can be separated by physical methods because dey are not chemically bound together.it can't be represented by a formula.example soil,urea,blood,sea water etc

SEPARATION TECHNIQUES
We ve already known dat mixture consists two or more different substances.these are d methods of separating them making use of d physical methods of their properties.
Sieving-used to separate mixture of different sizes.just like separating garri particles from d main garri.
Sublimation-this is a process whereby solids turn directly into vapour on heating without passing through liquid state.sublime substances like iodine nd ammonia chloride(NH4CL) can be separated through dis method.
Distillation- used to separate solvents from its solution.
Fractional distillation-used to separate miscible liquidsmaking use of their different boiling points.it is used in separation of crude oil.
Separating funnel-used in separation of two immiscible liquids like petrol nd water.it makes use of density.
Evaporation -used to recover a solid salute from a solution like salt from water.
Decantation-insoluble solid from a liquid

Mr Solution
Mr Solution
Now lets look at past question 2010( no 2) which of d following is an example of a mixture?
A common salt B blood C sand d washing soda .so mere looking at it u will c dat all of demi except blood are compounds. Common salt is NaCL,sand is SiO2nd washing soda is Na2CO3.10H2O bt blood has no formula because it has constituents which are not chemically bound together hence a mixture Ans is B

2004 no 1 when a solid substance disappears completely as a gas on heating,the substance is said to have undergone A evaporation B distillation C crystallization D sublimation. D answer is D because it turns directly to gas(vapour) according to our earlier explanation

Mr Solution
Mr Solution
Now lets look at ATOMS AND CHEMICAL EQUATIONS
As we ve known matter is made up of atom molecule nd ion.
Atom: smallest particle of an element dat can take part in a chemical reaction
molecule: smallest particle of a substance that can normally exist alone nd still retain d chemical properties of dat substance.NOTE:atoms combine to form molecules.the number of atoms in each molecule of an element is called ATOMICITY of d element.examples Ne Ar have 1 atomicity nd hence are monoatomic H2 N2 O2 have 2 atomicity nd hence are diatomic.
Ions:this is any atom or group of elements which possesses electric charge. Dey are of two types which are CATIONS(positively charged ions) nd ANIONS (negatively charged ions).note: any substance dat has d same number of negative nd positive ion is said to be electrically neutral.
We all know some symbols of elements like H He(helium) Na(sodium) etc

Relative atomic mass is d mass of an atom.
Relative molecular mass of an element or compound is the sum of the relative atomic masses of all d atoms in one molecule of d element.
Thus;R.M.M = sum of relative atomic masses of d atoms contained in d element or compound.
Example: calculate d relative molecular mass of Na2CO3 ( Na = 23, C=12, O = 16) solution: 1 molecule of Na2CO3 has 2 atoms of Na,1 atom of C nd 3 atoms of O
therefore, R.M.M of Na2CO3 =(2 * Ar(relative atomic mass) of Na 1 * Ar of C 3 * Ar of O)
=(2 * 23 1 * 12 3 * 16)
=46 12 48 = 106.
Hope u understand if u are confused in any way ask question

Mr Solution
Mr Solution
Lets continue from where we stopped yesterday.we ve talked about R.M.M.lets look into Molar Mass.
Molar mass(m.m):this is d mass of one mole of a substance expressed in grams.unlike relative molecular mass which has no unit,molar mass has unit nd its unit is g/mol.its just d same thing wit R.M.M just dat it has its own unit.so lets look at dis example

How many moles are there in 20g of CaCO3?(r.m.m of CaCO3 = 100)
from d unit of M.M which is g/mol
g/mol is d same thing as Gram/Mole
therefore Molar mass (M.M)= amount in gram/ concentration in mole
so from d question u can see dat
molar mass of CaCO3 = 100g
amount in gram of CaCO3 = 20g
number of moles or concentration in moles = ?
From d formula M.M = g/mole
we can make mole d subject of d formula which wen u cross multiply u have g= m.m * mole
so mole = g/m.m
which gives us mole =20/100 = 0.2mole.
Hope u understand any question?

Now lets look at percentage (%) by mass.dis can be calculated making use of d formula of d compound in question.

Calculate d % by mass of nitrogen in trioxonitrate(v) acid.(N = 14, H = 1, O = 16)
solution br /> note dat trioxonitrate(v) acid is HNO3
% by mass of an element = relative atomic mass(Ar) of d element /R.M.M of d compound * 100
so from dis formula % by mass of N in HNO3 =
remember dat HNO3 has 1 H, 1 N nd 3 O
Ar of N = 14
R.M.M of HNO3 = (1 * Ar of H plus 1 * Ar of N 3 * Ar of O)
= 1* 1 1 * 14 3 * 16 = 63g
63g of HNO3 have 14g of N
therefore % by mass of N = 14/63 * 100 = 22.2%

Jamb 2003 no 3.
What is d percentage by mass of oxygen in Al2(SO4)3.2H2O? ( Al = 27, S = 32, H = 1, O = 16)
A. 14.29% B.25.39% C.50.79% D.59.25%
solution
we ve already known d formula from what we said before
so we are talking about O here.
Looking at d compound Al2(SO4)3.2H2O contains 2 Al, 3S, 14 O, nd 4H.
Therefore Ar of O = 14 * 16 = 224
R.M.M of Al2(SO4)3.2H2O = (2 * 27 plus 3 * 32 plus 14 * 16 plus 4 * 1)=
54 plus 96 plus 224 plus 4 = 378
% by mass of O = 224/378 * 100 = 59.25%. So d answer is D.hope u understand.

63 is d relative molecular mass(R.M.M) of d compound HNO3.
As u can see HNO3 contains 1H, 1N nd 3 O.recall dat ( H = 1, N = 14, O = 16)
so R.M.M of HNO3 = ( 1 * Ar(relative atomic mass) of H plus 1 * Ar of N plus 3 * Ar of O)
= 1 * 1 plus 1 * 14 plus 3 * 16
= 1 plus 14 plus 48
= 63g.have u understood it now?

Mr Solution
Mr Solution
Valencies and Radicals
valency is d combining power of an element or radical.it is also known as an oxidation number bt we will know how to get it wen we do d periodic table

Actually metals show positive oxidation numbers while non metals exhibit negative oxidation numbers. E.g. H , O2- etc
radicals are formed as a result of few atoms of different elements coming together to react as a a single unit e.g. NH4 , NO2-
periodic table will do us better

Remember Atom is built up of three main types of solid particles which are proton(positively charged with mass number of 1) neutron(no charge nd mass number of 1) nd electron (negatively charged with mass number of 1/1840)
The number of protons in d nucleus of an atom is called ATOMIC NUMBER(Z).The sum of d proton nd neutron of an atom is called d MASS NUMBER(A).
The number of neutron = A-Z

Atoms of d same element having different number of neutron are called ISOTOPES.dey have d same atomic number bt different mass number.

Examples: chlorine has two mass numbers 35 nd 37 bt one atomic number of 17,Born has 10 nd 11 bt atomic number of 5.dat is while d mass no of some elements are not whole numbers.
Lets look at d calculations;

Chlorine exists in 2 isotopic forms 35 nd 37.d relative abundance of 35Cl = 75% nd 37Cl = 25%.calculate d relative molecular mass of Chlorine.
Solution
mass no. Of atom with 75% = 35
mass no of atom with 25% = 37
Ar of d element Cl =
(75/100 * 35) plus (25/100 * 37)
= 26.5 plus 9.25 = 35.5.any question?

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WHICH TIME D LECTURE START 2MORO

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Story Story
Story Story
] Atomic structure and
bonding



Fundamental Concepts

Atoms are composed of electrons, protons, and neutrons.
Electron and protons are negative and positive charges of
the same magnitude, 1.6 × 10-19 Coulombs.
The mass of the electron is negligible with respect to those
of the proton and the neutron, which form the nucleus of
the atom. The unit of mass is an atomic mass unit (amu) =
1.66 × 10-27 kg, and equals 1/12 the mass of a carbon atom.
The Carbon nucleus has Z=6, and A=6, where Z is the
number of protons, and A the number of neutrons.
Neutrons and protons have very similar masses, roughly
equal to 1 amu. A neutral atom has the same number of
electrons and protons, Z.


A mole is the amount of matter that has a mass in grams
equal to the atomic mass in amu of the atoms. Thus, a mole
of carbon has a mass of 12 grams. The number of atoms in a
mole is called the Avogadro number, Nav = 6.023 × 1023.
Note that Nav = 1 gram/1 amu.
Calculating n, the number of atoms per cm3 in a piece of
material of density d (g/cm3).
n = Nav × d / M
where M is the atomic mass in amu (grams per mol). Thus,
for graphite (carbon) with a density d = 1.8 g/cm3, M =12, we
get 6 × 1023 atoms/mol × 1.8 g/cm3 / 12 g/mol) = 9 × 1022 C/
cm3.

For a molecular solid like ice, one uses the molecular mass,
M(H2O) = 18. With a density of 1 g/cm3, one obtains n = 3.3
× 1022 H2O/cm3. Note that since the water molecule
contains 3 atoms, this is equivalent to 9.9 × 1022 atoms/
cm3.

Most solids have atomic densities around 6 × 1022 atoms/
cm3. The cube root of that number gives the number of
atoms per centimeter, about 39 million. The mean distance
between atoms is the inverse of that, or 0.25 nm. This is an
important number that gives the scale of atomic structures
in solids.
2.3 Electrons in Atoms
The forces in the atom are repulsions between electrons and
attraction between electrons and protons. The neutrons play
no significant role. Thus, Z is what characterizes the atom.
The electrons form a cloud around the neutron, of radius of
0.05 – 2 nanometers. Electrons do not move in circular
orbits, as in popular drawings, but in 'fuzzy' orbits. We
cannot tell how it moves, but only say what is the probability
of finding it at some distance from the nucleus. According to
quantum mechanics, only certain orbits are allowed (thus,
the idea of a mini planetary system is not correct). The
orbits are identified by a principal quantum number n,
which can be related to the size, n = 0 is the smallest; n = 1,
2 .. are larger. (They are "quantized" or discrete, being
specified by integers). The angular momentum l is
quantized, and so is the projection in a specific direction m.
The structure of the atom is determined by the Pauli
exclusion principle, only two electrons can be placed in an
orbit with a given n, l, m – one for each spin. Table 2.1 in the
textbook gives the number of electrons in each shell (given
by n) and subshells (given by l).
2.4 The Periodic Table
Elements are categorized by placing them in the periodic
table. Elements in a column share similar properties. The
noble gases have closed shells, and so they do not gain or
lose electrons near another atom. Alkalis can easily lose an
electron and become a closed shell; halogens can easily gain
one to form a negative ion, again with a closed shell. The
propensity to form closed shells occurs in molecules, when
they share electrons to close a molecular shell. Examples
are H2, N2, and NaCl.
The ability to gain or lose electrons is termed
electronegativity or electropositivity, an important factor in
ionic bonds.
2.5 Bonding Forces and Energies
The Coulomb forces are simple: attractive between electrons
and nuclei, repulsive between electrons and between nuclei.
The force between atoms is given by a sum of all the
individual forces, and the fact that the electrons are located
outside the atom and the nucleus in the center.
When two atoms come very close, the force between them is
always repulsive, because the electrons stay outside and the
nuclei repel each other. Unless both atoms are ions of the
same charge (e.g., both negative) the forces between atoms
is always attractive at large internuclear distances r. Since
the force is repulsive at small r, and attractive at small r,
there is a distance at which the force is zero. This is the
equilibrium distance at which the atoms prefer to stay.
The interaction energy is the potential energy between the
atoms. It is negative if the atoms are bound and positive if
they can move away from each other. The interaction energy
is the integral of the force over the separation distance, so
these two quantities are directly related. The interaction
energy is a minimum at the equilibrium position. This value
of the energy is called the bond energy, and is the energy
needed to separate completely to infinity (the work that
needs to be done to overcome the attractive force.) The
strongest the bond energy, the hardest is to move the
atoms, for instance the hardest it is to melt the solid, or to
evaporate its atoms.
2.6 Primary Interatomic Bonds
Ionic Bonding
This is the bond when one of the atoms is negative (has an
extra electron) and another is positive (has lost an electron).
Then there is a strong, direct Coulomb attraction. An
example is NaCl. In the molecule, there are more electrons
around Cl, forming Cl- and less around Na, forming Na+.
Ionic bonds are the strongest bonds. In real solids, ionic
bonding is usually combined with covalent bonding. In this
case, the fractional ionic bonding is defined as %ionic = 100
× [1 – exp(-0.25 (XA – XB)2], where XA and XB are the
electronegativities of the two atoms, A and B, forming the
molecule.
Covalent Bonding
In covalent bonding, electrons are shared between the
molecules, to saturate the valency. The simplest example is
the H2 molecule, where the electrons spend more time in
between the nuclei than outside, thus producing bonding.
Metallic Bonding
In metals, the atoms are ionized, loosing some electrons
from the valence band. Those electrons form a electron sea,
which binds the charged nuclei in place, in a similar way that
the electrons in between the H atoms in the H2 molecule
bind the protons.

Story Story
Story Story
Isotopes are variants of a particular chemical element
which differ in neutron number, although all isotopes of a
given element have the same number of protons in each
atom. The term isotope is formed from the Greek roots isos
(ἴσος "equal") and topos (τόπος "place"), meaning "the same
place"; thus, the meaning behind the name is that different
isotopes of a single element occupy the same position on
the periodic table. The number of protons within the atom's
nucleus is called atomic number and is equal to the number
of electrons in the neutral (non-ionized) atom. Each atomic
number identifies a specific element, but not the isotope; an
atom of a given element may have a wide range in its
number of neutrons. The number of nucleons (both protons
and neutrons) in the nucleus is the atom's mass number,
and each isotope of a given element has a different mass
number.
For example, carbon-12, carbon-13 and carbon-14 are three
isotopes of the element carbon with mass numbers 12, 13
and 14 respectively. The atomic number of carbon is 6,
which means that every carbon atom has 6 protons, so that
the neutron numbers of these isotopes are 6, 7 and 8
respectively.
Isotope vs. nuclide
Nuclide refers to a nucleus rather than to an atom. Identical
nuclei belong to one nuclide, for example each nucleus of
the carbon-13 nuclide is composed of 6 protons and 7
neutrons. The nuclide concept (referring to individual
nuclear species) emphasizes nuclear properties over
chemical properties, while the isotope concept (grouping all
atoms of each element) emphasizes chemical over nuclear.
The neutron number has large effects on nuclear properties,
but its effect on chemical properties is negligible for most
elements. Even in the case of the very lightest elements
where the ratio of neutron number to atomic number varies
the most between isotopes it usually has only a small effect,
although it does matter in some circumstances (for
hydrogen, the lightest element, the isotope effect is large
enough to strongly affect biology). Since isotope is the older
term, it is better known than nuclide, and is still sometimes
used in contexts where nuclide might be more appropriate,
such as nuclear technology and nuclear medicine.

Story Story
Story Story
What Are Isotopes?

Let's imagine a pair of identical twins. These twins have the
same temperament, and since they're identical, it is very
hard to tell them apart unless you examine them closely.
When it is time for their annual physical, the twins need to
step on a weighing scale, and when they do, one weighs
slightly more than the other. In terms of chemistry, we can
say that these twins are like isotopes of each other.

Story Story
Story Story
Difference between Nuclear Reaction and Chemical Reaction

1. While nuclear reaction takes place in the atom’s nucleus,
the electrons in the atom are responsible for Chemical
reactions.
2. The chemical reactions involve the transfer, loss, gain and
sharing of electrons and nothing takes place in the nucleus.
Nuclear reactions involve the decomposition of the nucleus
and have nothing to do with the electrons.
3. In a nuclear reaction, the protons and neutrons react
inside the nucleus and in chemical reactions the electrons
react outside the nucleus.
4. When comparing the energies, a chemical reaction
involves only low energy change, where as a nuclear
reaction has a very high-energy change.

yakubu ibrahim adam

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Mr Solution
Mr Solution
1. Matter has three basic states viz. Solid, Liquid and Gas
2. A physical change is one that can be reversible by
ordinary physical processes such as those separation
techniques outlined in your textbooks. While a chemical
change cannot.
3. All chemical reaction occur within the electrons of atoms
but nuclear reaction occur within the nuclei of atoms.
4. An atom is not identified by the number of electrons it
posses but by that of protons.
(1) anything that can occupy space and has mass in the
sense that it is made up of particles of any size is refer to as
matter. Matter can be created and destroyed. When atoms
of radioactive isotopes decay, they undergo destruction
leading to the formation of new atoms of entirely different
elements through a process known as nuclear fission.
Similarly atoms of very light isotopes such as those of
hydrogen can be fused together to produce a new atom. In
this sense matter is created and likewise can also be
destroyed.
(2) Although it may be familiar to us that matter generally
compose of either atoms, molecules, ions or a combination
of any of the above. But it is very important to note that a
substance is said to be a molecule due to the fact that it
function as a"unit"and may have chemical characteristics
either similar to (as in the case of oxygen gas) or entirely
different from the atoms in it e.g H2O. While ions are any
atoms or molecules that posses charge. In a nutshell, both
molecules and ions are made up of atoms. It follows that
atoms are the (fundamental) building block of matter.
(3) During a chemical reaction, certainly, it's possible to
obtain a new mixture from a combination of compounds
formed from the reaction if the compounds formed could
remain in the solution (whether true or false) without
reacting with each others. This new mixture is different from
the mixture formed by some of the compounds of the
reactants before the reaction is induced on the system
(some thermal activated reactions will be adequate to
explain this better). Physical change can also bring about the
formation of new mixtures but in this case the mixtures are
not products of the reactant but instead are merely formed
by addition of new substances to the initial mixtures.
(4) Mortar is a mixture of sand, lime (calcium hydroxide) or
cement and water. On exposure to air for some time, the
lime react with atmospheric carbon(iv)oxide to produce
calcium trioxocarbonate(iv) that fuse sand together and the
mortar is set.
When egg is boiled the protein in it will be denatured due to
temperature tolerance that cause the cleavage or twist of
hydrogen bonds or peptides linkage in the protein, leading
to the clumping of the protein into a solid mass. Boiling of
egg Is not a chemical change.
(5) Physical Change can easily be separated by ordinary
separation techniques. e.g a mixture of iron scraps and sand
can be separated using a magnet.
(6) Ice can float on water because of physical change on the
bonds. The change on the bonds of water is induce by
temperature. The structure of the bonds of ice is different
from that of water in the sense that that of ice is opened.
NB: only bonds are being twisted not that a new compound
is in ice compare to what is in water.
(7) phosphorylation of glucose is not a physical change. It is
a reaction catalyzed by hexokinesis, an enzyme that catalyze
the conversation of glucose to glucose-6-phosphate in
glycolysis.
(8.) D
(9) sound has no particle in it. It is merely a vibration that
leads to the transfer of energy in the form of wave.
Flavour is a seasoner.
(10) iodine is a solid at room temperature. This solid usually
convert to vapour without any transient liquid state and thus
it is said to undergo sublimation.

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Tanx for this pleasant [email protected] a serenity inspiration

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Pls is there any show for next tomorrow jamb exam ? Eng, Biology , Chemistry and Physics. My name is Ugoo

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Thanks 4 ur assistant @ solution class.

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Lecturers in charge - Promzyguru

OVER TO YOU NOW
[/quote][/color]

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Tnx for ur compliment

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Originally posted by Guest
Kelvin
are u kelvin ibrahim

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Peter by name pls mr solution tomorrow is chemistry how can I get it

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I need chemistry practical tomorrow pls help me from adex

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harnike005


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