Chemistry

Salts and Types of Salt in Chemistry

Olawunmi Omosanya - Wed, 10th July, 2019 @ 16:52: PM

Topics in Chemistry

Salts and Types of Salt in Chemistry Separation Techniques Separation Techniques part 2 Separation Techniques part 3 Physical Change, Chemical Change, Element, Compound and Mixture Electrolysis, Electrolyte, Electrode, Anode and Cathode Grahams law of diffusion Physical Properties of Metals Daltons Atomic Theory and its Modifications Periodic table and Classification of Elements



Academic Questions in Chemistry

The only metal that exist as liquid at room temperature is _____.

  1. Nickel
  2. Duralumin
  3. Mercury
  4. Lead
  5. Titanium
  6. Cesium

ANSWER is Mercury

Mercury is a liquid metal at room temperature. Its chemical symbol is Hg. The name mercury comes from its Greek name, hydrargyrum, which means "liquid silver" .  Mercury has an atomic number of 80. Please read on the periodic table of elements here

The element mercury is also considered to be named after the fastest-moving planet in the solar system. You can read on solar system here.

Chemistry

What is a Salt?

Almost everyone would have used the word “salt” when it comes to cooking. This ‘cooking’ salt or better still table salt or common salt is just one of the many salts we have in chemistry.

Chemically, this table salt or common salt is referred to as Sodium Chloride

Sodium chloride has the chemical symbol "NaCl"

Note: NaCl is naturally present in sea water; and they often give rise to the salt water habitat which happens to be home to some organisms.

Generally, a salt can be defined as a compound/substance composed of a positive metallic ion and a negative non metallic ion.

For 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.

Please read on ions here.

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 are produced).

 

Types of Salt

1. Normal Salt

A normal salt is formed from an acid and a base. It is electrically neutral.

By definition, a normal salt is the product formed when an acid react with a base.

The acid and the base must be of equal strength; for instance, a strong acid reacting with a strong base.

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 hydrogen ion as its only positive ion; so for a normal salt to be formed, all the hydrogen ions must be replaced by the metal 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) while the metallic ion (Na+) replaced the hydrogen in (HCl acid) to form NaCl. For this reason, the normal salt is electrically neutral.

 

2. Acid Salt

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.

For 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 on the other hand will form an acid salt since it is dibasic.

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).

 

3. Basic Salt

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

 

4. Double Salt

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 [Aluminium Potassium tetraoxosulphate(VI) dodecahydrate] or KAl(SO4)2.12H2O and [Ammonium Iron(II) tetraoxosulphate(VI) hexahydrate] or (NH4)2 Fe(SO4)2.6H2O.

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)2.6H2O will ionize to produce Ammonium ion (NH4+), Iron (II) ion (Fe2+) and sulphate ion (SO42-) respectively.

 

5. Complex salt

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- 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- that makes K4Fe(CN)6 a complex salt.

 

It is also important to add that salts can also be formed when:

  • Metal reacts with an acid: Hydrogen gas is given off during this process. Consider the equation below:

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.

 

  • Acid reacts with carbonates: Carbon(IV)oxide (CO2) and water (H2O) are always given off during this reaction.

2HCl(aq) + Na2CO3(s) -> 2NaCl(s) + H2O(l) + CO2(g)



Amazing facts in Chemistry

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

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