Molarity & Molar solution

Molarity is a chemical unit used to express the concentration or strength of a solution. What do you mean by molarity?
Definition for molarity
Molarity is the number of moles of solute present in one litre of the solution. In general we can say that
Molarity of the solution=Number of moles of the solute/Volume of the solution in litres
Also we can say that if w is the weight in grams of solute dissolved in V litres of the solution & if M is the gram molecular weight of the solute, then we can say that
Molarity= w/MV
Definition for one molar solution
One molar solution means it contains one mole of the solute dissolved in one litre of the solution.

Solution,Solvent & Solute

Do you know what are solutions, solvents & solutes? A homogeneous mixture of two or more substances is known as solutions . It is important to note that solute is the substance present in minor quantities & solvent is the substance present in larger proportions.

Normality & Normal solution

Every chemistry students should be familiar with these terms. Actually what is normality? First remember that normality is a chemical unit used to express the concentration of a solution. Do you know the definition for normality?
Definition for normality
Normality is the number of gram equivalent of the solute present in one litre of the solution. In general we can say that
Normality of the solution=Number of gram equivalent of solute/Litres of solution.
Also it is important to note that if w is the weight in gram of the solute & E is the equivalent weight of the solute present in V litres of the solution, then
Normality of the solution =w/EV
We can prove this by the following problems:
Problem 1:

How can we calculate the number of grams of solute in 300ml of 1.5N NaOH solution?

Solution:

Given normality=1.5 N

Volume of the solution= 300ml= 0.3 litre=V

Equivalent weight of NaOH =40=E

So here the equation used is Normality of the solution= w/EV

Therefore w=1.5*40*o.3=18 gram

Problem 2:

How can we calculate the normality of a solution containing 224gram KOH in 2 litre of the solution?

Solution:

Normality=Number of gram equivalent of the solute/Volume of the solution in litre

Here volume = 2 litre

Number of gram equivalent of the solute=224/56=4

Therefore normality=4/2=2N

Definition for one normal solution

One normal solution means it contains one gram equivalent weight of the solute per litre of the solution.

Mole fraction of a solute

What is mole fraction of a solute? This is the ratio of number of moles of the solute to the total number of moles present in the solution. In general we can say that
Mole fraction of the solute= Number of moles of the solute/Total number of moles present in the solution
For example : Do you know how to calculate the mole fraction of CH₃OH in a solution which contains 64gram of CH₃OH in 144 gram of H₂O?

• CH₃OH is methanol. So mole fraction of methanol is calculated using the above equation. That means number of moles of solute= 64/32=2
• Total number of moles present in the solution=( 64/32) + (144/18) = 2+8=10
• Mole fraction of methanol=2/10=0.2

Fehling's solution

What do you mean by fehling's solution? This is an alkaline solution of a complex copper tartrate & is prepared by adding a solution of CuSO₄ to an alkaline solution of Rochelle salt. Do you know what is rochelle salt? Rochelle salt is sodium potassium tartrate. Remember that this solution is violet in colour . On warming with aldehyde this is reduced to a red precipitate of Cu₂O.

Fenton's reagent

Chemistry students should be familiar with some important reagents. This post is about fenton's reagent. It is important to note that fenton's reagent is a mixture of ferrous sulphate & hydrogen peroxide. For the oxidation of ethylene glycol to glycol aldehyde, fenton's reagent is used.

An alloy of iron & carbon containing 0.1 to 1.5% carbon is

Steel

How lead is isolated from the sulphide ore?

• By air reduction method

Calamine contains

Zinc

Name the concentration method used for sulphide ores

• Froth floatation

Duralumin is an alloy of

• Al, Mg, Cu, Mn

Stainless steel contains

• Fe, Cr, Ni

White lead

2PbCO₃.Pb(OH)₂

Give an example of a substance which absorbs carbondioxide from air & gives oxygen

• Ozone

Name the process used to prepare Fe

• Aluminothermic process

18 carat gold contains

• 75% gold

Plaster of paris is prepared from

• Gypsum salt

The dual nature of electrons was put forward by

• Louis de broglie

What is the name given to the space within an atom where there is maximum probability of finding an electron ?

• Orbital

What is the shape of the p orbital?

• Dumb bell

In german 'Aufbau' means

• Build up

What is the number of degenerate orbitals in d sublevel?

• 5

Name the orbital with the greatest number of possible orientation?

• f

Shape of the orbital is determined by which quantum number?

• Azimuthal

Important Note

• Orbitals with the same energy are said to be ..........

Answer is degenerate.

What is the electronic configuration of chromium?

1s²2s²2p⁶3s²3p⁶3d⁵4s¹

Give the number of umpaired electrons in a Helium atom

• No unpaired electrons

Sublimation

Sublimation is an important process for the purification of organic compounds. That means from non volatile substances, volatile organic compounds are separated by this process.

• What do you mean by sublimation?

Sublimation is the direct conversion of solid into a vapour state. Examples of substances having sublimation property are dry ice, iodine,naphthalene, camphor etc.

Fractional crystallisation

This is a process used in the purification of organic compounds. Suppose there are two solids with different solubilities. And they are soluble in the same solvent, then fractional crystallisation is used to separate them.

3-phenyl prop-2-enoic acid is the IUPAC name of

• Cinnamic acid

What is the IUPAC name of urea?

• 1-amino methanamide

which is the acid obtained when P4O10 is dissolved in cold water?

• metaphosphoric acid, HPO₃

Give the formula for oleum

• H₂S₂O₇

What is oleum?

• Fuming sulphuric acid

What is the commercial name for sodium hexametaphosphate?

• Calgon

Superphosphate of lime

• Ca(H₂PO₄)₂ + CaSO₄

Define acid & base according to lewis theory

According to Lewis theory, an acid is an electron pair acceptor & base is an electron pair donor.

What do you mean by etching?

An example of silicate material is glass. Remember that silica is represented as SiO₂.So compounds containing silica & silicates are attacked by hydrogen fluoride gas or its aqueous solution. When reacted with HF gas, SiF₄ gas is evolved. This is represented as

SiO₂ + 4HF--->2H₂O + SiF₄.

But in solutions H₂SiF₆ is formed. This is given as

SiO₂ + 6HF----> H₂SiF₆ + 2H₂O.

Etching means the attack of HF on glass.

Hydrogen diffuses faster than chlorine. why?

• This is based on graham's law of diffusion. That means gases with low molecular weight or low density diffuses fast. In the case of hydrogen molecular weight is 2 & for chlorine gas it is 71. So hydrogen diffuses more faster than chlorine.

What is fenton's reagent?

• Fenton's reagent is a mixture of Fe²⁺ & H₂O₂.

When comparing p-nitrophenol & o-nitrophenol which is a stronger acid & why?

• p-nitrophenol is a stronger acid than o-nitrophenol. This is because in o-nitrophenol intramolecular hydrogen bonding is present which makes o-nitrophenol a weaker acid.

Li resembles Mg in properties although they belong to different groups. Why?

• This is because of diagonal relationship. Also they have the same atomic size.

In fire extinguishers CCl4 is used. why?

• The important property of CCl₄ vapours is that they are non-inflammable. Due to this property they are used in fire extinguishers.

Concentrated nitric acid turns skin yellow. why?

• This is because concentrated nitric acid converts protein into yellow xanthoproteic acid & so the skin turns yellow.
• Nitric acid is represented as HNO₃.

Orthophosphoric acid is tribasic but phosphorous acid is dibasic. why?

• Orthophosphoric acid is H₃PO₄ & phosphorous acid is H₃PO₃.
• In orthophosphoric acid there are three hydrogen atoms linked to oxygen atoms but in phosphorous acid there are two hydrogen atoms bonded to oxygen atoms while the third hydrogen atom is directly linked to phosphorous. So orthophosphoric acid is tribasic & phosphorous acid is dibasic.

Give reasons

Cuprous chloride is diamagnetic while cupric chloride is paramagnetic. why?

• Cuprous ion is represented as Cu⁺ & cupric ions is represented as Cu⁺⁺. The electronic configuration of cuprous ion is 1s²2s²2p⁶3s²3p⁶3d¹⁰.Here we can see that there are no unpaired electrons . So they are said to be diamagnetic in nature.
• The electronic configuration of cupric ions is 1s²2s²2p⁶3s²3p⁶3d⁹. It is important to note that here there is one unpaired electron. So cupric ions are paramagnetic in nature.

Chloroform is stored in dark colored bottles. why?

This is because in the presence of air chloroform is oxidised to phosgene. To prevent the formation of phosgene, they are stored in dark colored bottles.
CHCl₃ + 1/2 O₂ ---->HCl + COCl₂.

Phosgene is represented as COCl₂. This is poisonous.

What are isotonic solutions?

Solutions which have the same osmotic pressure are called isotonic solutions.

Living in an atmosphere of CO is dangerous. Why?

• This is because CO combines with haemoglobin & forms carboxyhaemoglobin which is incapable of carrying oxygen.

Atom is said to be electrically neutral. why?

• In an atom equal number of positively charged protons & negatively charged electrons are present. So they are said to be electrically neutral.

Zinc is able to displace silver from AgNO3 solution. why?

The oxidation potential of zinc is more positive than that of silver. So zinc is able to displace silver from AgNO₃ solution.

What are the characteristics of buffer solutions?

• Definite pH
• It is important that the pH value should remain steady on keeping or on dilution or on adding small amount of acid or alkali to it.