Topics in ChemistryCompounds 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 Mixtures and Separation of Mixtures Mixtures and Separation of Mixtures - part 2 Mixtures and Separation of Mixtures - part 3 Physical Change and Chemical Change Concept of Ions and Electrolytes Grahams Law of diffusion, Worked Example and Importance
Academic Questions in Chemistry
Which of the following is NOT a characteristic of chemical change?
Which of the following statement is FALSE concerning a physical change _____.
The following substances will sublime EXCEPT _____.
Which of the following is a state of matter?
The ideal way of separating a mixture of blood is through _____.
Which of the following separation technique is used to separate an insoluble solid that sediments in a liquid?
A _____ mixture is said to be uniform all through.
The reaction involving an acid and a base is termed _____.
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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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. Please read some interesting facts about gold here
Copper is the only metal that is naturally antibacterial. This is why you would see some children carry copper water bottles to school
Water actually 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.
Please read on modification of Dalton's atomic theory here.
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