MOLE-MOLE ANALYSIS:

Mole Concepts:

Mole and Moles Analysis rule:

Ratio of Moles of reactant or product with its coefficient is always constant for a balance chemical equation:

ILLUSTRATIVE EXAMPLE (1):

ILLUSTRATIVE EXAMPLE (2):

ILLUSTRATIVE EXAMPLE (3):

ILLUSTRATIVE EXAMPLE (4):  367.5 gm KClO₃ (122.5) when heated then calculate.

(1) How many gram of O₂ is produced?

(2)How Many litre of O₂ is produced at STP?

SOLUTION:

ILLUSTRATIVE EXAMPLE (5): how many moles O₂ are required to needed produced 5 moles of Fe₂O₃.

SOLUTION:

ILLUSTRATIVE EXAMPLE (6): how many grams of Fe₂O₃ formed by heating of 18 gm FeO with O₂.

SOLUTION:

PERCENTAGE(%) YIELD OF CHEMICAL REACTION:

ILLUSTRATIVE EXAMPLE (1): 200 gm of CaCO₃ on heating produces 11.2 litre of CO₂ (g) at STP calculate % yield of reaction?

ILLUSTRATIVE EXAMPLE (2): 3.9 gm Al(OH)₃  is reacted with excess of HCl , 6.5 gm AlCl₃ is formed determined % yield of reaction ?

ILLUSTRATIVE EXAMPLE (3): Calculate moles of D produce by 4 moles of A.

ILLUSTRATIVE EXAMPLE (4): 9 moles of D and 14 moles of E are allowed to react in closed vessel according to given equation.

Calculate number of B formed in end of reaction, If 4 moles of G are present in reaction vessel. (% yield of each reaction in the reactions)

ILLUSTRATIVE EXAMPLE (5): For the reaction
Initially 2.5 moles of Fe(NO₃)₃ and 3.6 moles of Na₂CO₃ are taken. If 6.3 moles of Na₂CO₃ is obtained the % yield of given reaction is ?

PERCENTAGE(%) PURITY OF GIVEN SAMPLES:

LLUSTRATIVE EXAMPLE (1): 200 gm of CaCO₃ sample on heating produces 11.2 liters of CO₂ (g) at STP. Calculate % purity of CaCO₃ sample?

LLUSTRATIVE EXAMPLE (2): Calculate the amount of 80 % pure NaOH sample required to react with 21.3 gm Chlorine in hot condition.

LLUSTRATIVE EXAMPLE (3): When 1.25 gm sample of Chalk is strongly heated. 0.44 gm of CO2 is produced. Calculate % purity of Chalk sample?

LLUSTRATIVE EXAMPLE (4): The Mass of 80% pure H₂SO₄ required to completely neutralize 106 gm of Na₂CO₃?

LLUSTRATIVE EXAMPLE (5): When dilute HCl is added to 5.73 gm of contaminated CaCO₃, 2.49 gm of CO₂ is obtained. Find % purity of CaCO3 sample?

LLUSTRATIVE EXAMPLE (6): A sample of impure Iron pyrite (FeS₂) when 13.9 gm heated then it produces iron (iii) oxide (Fe₂O₃) and Sulphur dioxide (SO₂). If 8.02 gm Iron (iii) oxide is obtained, what was the % purity of given sample (original-FeS₂)?

PERCENTAGE (%) AVAILABLE CHLORINE IN BLEACHING POWDER:

Bleaching powder is not a true compound but it is a mixed salt of calcium hypochlorite [Ca (OCl) ₂].3H₂O and basic calcium chloride [CaCl₂Ca (OH) ₂H₂O]. [Simply it is represented by CaOCl₂.
The bleaching action of [CaOCl₂] is due to liberation of oxygen with limited quantity of dilute acid.                                                                                                        

Whereas disinfectant action available of Cl₂ on reaction with excess of acid.

The Chlorine liberates is called available Chlorine, and calculation of available Chlorine is called IODOMETRY.

IODOMETRIC-CALCULATION OF AVAILABLE % CHLORINE: Take a W (gm) sample of bleaching powder; and  when bleaching powder treated with dilute acid or water then liberates chlorine gas.

The chlorine produced in above reaction is titrated with KI solution which produced (I₂) Iodine which is further completely titrated with hypo solution.                                          

If number of millimoles of hypo solution consume is M V then millimoles of %available chlorine is calculated as ;

                            Millimoles of Iodine is =1/2 Millimoles Hypo solution

                            Millimoles of Iodine is = Millimoles chlorine

Weight of available chlorine is = Number of moles x molecular Wt of Chlorine 

ILLUSTRATIVE EXAMPLE(1): If trace of chlorine are not remove from pulp used for paper manufacturing , then on the long standing it weaken the paper and makes it yellowish , which of following antichlor can be used to remove chlorine from pulp ?.
(A) Na₂S₂O₃        (B) conc. HCl            (C) NaHCO₃           (D) Both (A) and (B)

SOLUTION:

An antichlor  is a substance used to decompose residual hypochlorite or chlorine after use of chlorine based bleaching , in order to prevent ongoing reactions .example s of antichlor – Sodiumbisulphite (NaHSO₃), Pottassiumbisulphite (KHSO₃) ,  Sodiummetasulphite (Na₂S₂O₃), Sodiumthiosulphate  (Na₂S₂O₃) and hydrogen peroxide (H₂O₂).

ILLUSTRATIVE EXAMPLE (2): Available chlorine in sample of bleaching powder can be calculated as per the following reactions.

If 4 gm of bleaching powder dissolved to give 100 ml solution 25 ml of it react with excess of CH₃COOH and KI .The Iodine liberation required 10 ml of 0.125 N Hypo solutions. Calculate % of available chlorine in the sample.
(A)  21%                       (B) 35 %                     (C) 45 %             (D) 4.4%

SOLUTION:

ILLUSTRATIVE EXAMPLE (3): Calculate the % of available chlorine in the sample in a sample of 3.35 gm of bleaching powder which was dissolved to 100 ml water. 25 ml of this solution on treatment react with KI and dilute acid. Required  20 ml 0.125 N Hypo solution (Sodiumthiosulphate- Na₂S₂O₃). 

SOLUTION:

ILLUSTRATIVE EXAMPLE (4): 25 ml of household bleach solution was mixed with 30 ml of 0.50 M KI and 10 ml of 4.0N acetic acid. In this titration of the liberated iodine 48 ml of 0.25 N Na₂S₂O₃ was used to reach the end point. The Molarity of household bleach solution is?
SOLUTION:

VOLUME STRENGTH OF H2O2(aq)

 Hydrogen peroxide is a colourless liquid used as bleaching agent in some food and act as oxidising as well as reducing agent.The most common use of hydrogen peroxide is in cosmetic including personal care, hair dye, bleach shampoos conditioners and first aid  antiseptic.
Hydrogen peroxide also used as propellant for torpedoes on account of its exothermic decomposition.

The strength of Hydrogen peroxide expressed several ways like Volume strength, W/V % (% strength), Molarity, Normality etc.

COMMERCIAL LABELLING OF H₂O₂ AS ‘X’ VOLUME :  

Commercially H₂O₂ labelled as 'X' volume H₂O₂ (at P=1 ATM and T=273 K)
Where 'X' may be  10V, 20V, 30V, 40 V etc. 

Here  'X' Volume H₂O₂ means that 1ml of such solution of hydrogen peroxide on decomposition  produce 'X' ml of oxygen (at P=1 ATM and T=273 K).

For example 10 Volume H₂O₂ means that 1ml of such solution of hydrogen peroxide on decomposition  produce '10' ml of oxygen (at P=1 ATM and T=273 K).

W/V % or PERCENTAGE STRENGTH OF  H₂O₂SOLUTION: 

The amount of H₂O₂ in gram present in 100 ml of aqueous solution of H₂O₂. Called (w/v) or percentage strength.

Illustration:  taken 10 V (Vol) H₂O₂:

By Stoichiometric calculations:

Thus 1ml, 10 V labelled H₂O₂ (aq) solution contains 0.0303 gm H₂O₂.

Similarly 100 ml, 10 V labelled H₂O₂ (aq) solution contains 0.0303x100=3.03 gm of H₂O₂. This called W/V % or percentage strength of H₂O₂ solution.

MOLARITY AND NORMALITY OF H₂O:

 And 1000 ml, 10 V labelled H₂O₂ (aq) solution contains 0.0303x1000=30.30 gm H₂O₂. It means 30.30 gm H₂O₂ dissolved in 1000 ml (1L) Solution.

  Hence Molarity of 10 V H₂O₂ Solution is = 0.89 M

  Normality of 10V H₂O₂ (aq) Solution: 

Hence Normality of 10 V H₂O₂ Solution is =1.79 N

 We also know that NORMALITY= MOLARITY X n-FACTOR

                              Normality= O.89x2 =1.79 N

ALTERNATIVE MATHAD TO DTERMINED MOLARITY AND NORMALITY:

Volume of O₂ provided by 1unit Volume of H₂O₂ aq Solution

ILLUSTRATIVE EXAMPLES:

EXAMPLE: (1) A solution of H₂O₂ has Normality N/1.7 calculate w/V strength of this solution?.
EXAMPLE: (2) Convert 20 V H₂O₂ into % strength or w/v strength?
EXAMPLE: (3) Convert 6.8 % strength of H2O2 into Volume strength?
EXAMPLE: (4) 500 ml of a H₂O₂ solution on decomposition produce 2 mole of H₂O. Calculate the Volume strength of of H₂O₂ of solution? (Given Volume of O2 measured at 1atm and 273 K)  (Ans - 44.8 V)
EXAMPLE: (5) What is the percentage strength of "15" volume of H₂O₂?
EXAMPLE: (6) What volume of H₂O₂ solution of "11.2 volume strength is required to liberate 2240 ml of O₂ at NTP?
EXAMPLE: (7) 30 gm Ba(MnO₄)₂ sample containing inert impurity completely reacting  with 100 ml "28" volume strength of H₂O₂ in acidic medium then what will be the percentage purity of Ba(MnO₄)₂ in the sample ?. (Ba=137, Mn = 55, O =16)
EXAMPLE: (8) the strength of "20 Volume" H₂O₂ is equal? 
EXAMPLE: (9) What is weight of available oxygen from a solution of H2O2, if 20 ml of this solution need 25 ml, N/20 KMnO4 for complete oxidation? (Ans- 0.25)
EXAMPLE :( 10) calculate molarity of 44.8 V strength of H₂O₂ aq Solution?.

EXAMPLE: (11) calculate the molarity of H₂O₂ if 11.2 ml H₂O₂ require 30 ml of 0.5 M K2Cr2O7 for its complete oxidation; also calculate the Volume strength of H₂O₂? (Ans M=45/11.2 and volume strength=45)