Topics in ChemistryLe 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 Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry
Academic Questions in Chemistry
Which of the following isn't an element of the periodic table.
According to the periodic table, elements in the same group have got the same number of shells.
The periodic table of elements is also called the Mendeleev's table.
The simplest formula of a compound is termed _____.
A. Emperical formula
B. Molecular formula
C. Avogadro's number
D. Mass formula
E. Molar mass formula
F. Mole ratio
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)
Which of the following statement is false concerning hydrocarbons?
A. Hydrocarbons can be aromatic
B. Hydrocarbons are made up of carbon and hydrogen only
C. Alkynes are aliphatic hydrocarbons
D. Alkenes have a carbon-carbon double bond in their structure
E. Benzene ring has a carbon-carbon triple bond in its structure
F. Hydrocarbons are the main constituents of petroleum and natural gas
The ability of carbon to form long chain of itself is called _____.
A. Carbon chain reaction
E. Organic chemistry
F. Carbon moleculation
Calculate the relative molecular mass of methane. (Carbon = 12.001, H = 1.00794).
A. 13.00894 amu
B. 11.00206 amu
C. 12.00794 amu
D. 14.001 amu
E. 15.001 amu
F. 16.033 amu
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At one point or another, we must have used a popular kind of “salt” in cooking our food. This "cooking salt" or better still table salt or common salt as it's called is just one of the many salts we have in chemistry.
Chemically, this table salt or common salt is referred to as Sodium Chloride. It's chemical formula is "NaCl".
Note: NaCl is naturally present in the oceans and seas which makes up the salt water habitat. This habitat serves as a home to numerous organisms.
Generally, a salt can be defined as a compound/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.
In the laboratory, salts can be prepared in a variety of ways and as a result, salts are of different types.
Note: 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 explanations on the various types of salt. These are:
A normal salt is formed from an acid and a base.
By definition, a normal salt is the product formed when an acid reacts with a base.
The acid and the base must be of equal strength. For instance, a strong acid will have to react with a strong base in the formation of a normal salt.
Note: This reaction involving an acid and a base is known as neutralization reaction. The other product formed from 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.
Note: 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 (H+) from the acid reacts with the hydroxide ion (OH-) from the base to form water (H2O). Simultaneously, the metallic ion (Na+) replaced the hydrogen in (HCl acid) to form NaCl. For this reason, the normal salt is electrically neutral.
A normal salt is electrically neutral since the number of hydrogen ions (H+ from the acid) that reacts with those of the hydroxide ions (OH- from the base) are always equal.
Note: It is also important to add that normal salts can be formed when:
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.
2HCl(aq) + Na2CO3(s) -> 2NaCl(s) + H2O(l) + CO2(g)
For an acid salt to be formed, only a part of the hydrogen ions in the acid is replaced; and as a result, hydrogen ion is always present in an acid salt. In fact, it is presence of hydrogen ion (H+) in the salt that makes it an acid salt.
Note: 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 only one replaceable hydrogen within it.
Hydrogen tetraoxosulphate(VI) acid (H2SO4) is dibasic since it has two replaceable hydrogen ions within its molecule.
From our explanation above; it is quite clear that HCl will not be able to form an acidic salt since it’s monobasic.
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)
Note: One of the hydrogen ions from the acid H2SO4 had been replaced by Sodium (Na).
Unlike an acid salt which contains hydrogen ion (H+) within it, 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.
Note: 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, out of which 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 be: Potassium ion (K+) which is positively charged, Aluminium ion (Al3+) which is positively charged and Sulphate ion (SO42-) which is negatively charged.
Similarly, (NH4)2 Fe(SO4)2.6H2 will ionize to produce Ammonium ion (NH4+), Iron (II) ion (Fe2+) and Sulphate ion (SO42-).
Any salt that contains complex ions within it is regarded as a complex salt.
For now, just imagine complex ions to 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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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.
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Amazing facts in Chemistry
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
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:
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:
Organic chemistry is the study of carbon and it's compounds.
Carbon is the focus of organic chemistry because it has a wide chemical diversity in the sense that it can combine with other carbon atoms to form a long chain of carbon molecule. This ability and process whereby carbon can form a long chain of itself is called catenation.
A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.
Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.
The large molecules (above) have no specific chemical formula throughout their volume.
Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the modifications of Dalton's atomic theory.
Calculate the Relative Molecular Mass of methane (CH4). (Carbon=12.001 and H=1.00794)
Molecular Mass = Atomic mass of carbon + Atomic mass of Hydrogen
Methane is composed of one atom of Carbon and 4 atoms of Hydrogen.
12.001 + (1.00794 x 4)
Molecular Mass of Methane = 16.033 amu
Calculate the Relative Molecular Mass of water (H2O). (Oxygen=15.9994 and Hydrogen=1.00794)
Molecular Mass = Atomic mass of Hydrogen + Atomic mass of Oxygen
Water contains 2 atoms of Hydrogen and 1 atom of oxygen.
(1.00794 x 2) + 15.9994
Molecular Mass of Water = 18.015 Da
Below are some facts about gold:
It is the only metal that has a gold (golden) color
Gold is present inside the earth crust in all the seven continents
Pure gold is soft and very stretchable (It can even be stretched into threads)
The Latin name of Gold is aurum which means 'shining dawn'. For this reason, its chemical symbol is 'Au'
Gold is a very good conductor of electricity. This is why it’s sometimes used in making USB and audio cables
Gold is non toxic and can be eaten with food. It is sometimes added to desserts in some expensive restaurants
The term Gold originated from an ancient English word 'geolu' which means yellow
24karat gold is the purest gold element