Welcome to Chem Zipper.com......: February 2019

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Thursday, February 28, 2019

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:

Monday, February 25, 2019

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 ?

Sunday, February 24, 2019

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 (FeS2when 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)?

Wednesday, February 20, 2019

HEISENBERG'S UNCERTAINTY PRINCIPLE:

"It is not possible to determine simultaneously the exact position and exact moment of a particle as small as an electron"
ILLUSTRATIVE EXAMPLE (1): If error in position of an electron is 0.33 pm, what will be the error in its velocity? (1 pm=10-12

ILLUSTRATIVE EXAMPLE (2): If H+ (ion) is accelerated to a final velocity of 6.62×10+6 meter per second and error in velocity is 1% then find uncertainty in position is?
ILLUSTRATIVE EXAMPLE (3): Radius of nucleus is the order of 10-13 cm (10-15 m) and thus on the basis of Heisenberg's uncertainty principle .show that electron cannot exist within the atomic nucleus?
SOLUTION:
ILLUSTRATIVE EXAMPLE (4): If uncertainty in position and momentum of electron  are equal then prove that uncertainty in velocity  is ...
SOLUTION:
ILLUSTRATIVE EXAMPLE (5):If uncertainty in momentum of an electron are three times of uncertainty in position then uncertainty in velocity of electron would be  
SOLUTION:
ILLUSTRATIVE EXAMPLE (6): What is the uncertainty of Photon in position of  wave length 500 A .If wave length is known to an accuracy of 1pm. 
SOLUTION:
ILLUSTRATIVE EXAMPLE (7): An electron is accelerated by (V) volt and following graph is obtained calculate the (V) voltage?
SOLUTION:
ILLUSTRATIVE EXAMPLE (8): A electron having velocity 2×10+6 m/s has uncertainty in kinetic energy is 6.62/π×10-34 j, than calculate the uncertainty in position of electron in Anstrom .
SOLUTION:
ILLUSTRATIVE EXAMPLE (9): Two particles A and B are in motion .if the wave length associated with particle A is 5×10-8 m. Calculate the wave length associated with particle B if momentum is Half of A?
SOLUTION:
ILLUSTRATIVE EXAMPLE (10): If uncertainty in position of an moving electron is equal to its de Broglie wave length, then its velocity will be completely uncertain. Explain?
SOLUTION:
ILLUSTRATIVE EXAMPLE (11): If the de Broglie wave length of a particle of mass (m) is 100 times of its Velocity. Then its value in term of its mass (m) and plank constant (h) is?

Saturday, February 2, 2019

DIBORANE-HYDRIDE OF BORONE-(B2H6):

INTRODUCTION:
Boranes are hydride of Boron and diborane is famous borane. It is gas and is highly inflammable in air and poisonous Diborane is used for preparing substances such as high energy fuel and propellants.
The main boranes are Nidoborane and Archanoborane.
Nidoborane (BnHn+4): Example B2H6, B3H7, and B4H8
Archanoborane (BnHn+6):  Example B2H8
Boranes are hydride of Boron and diborane is famous borane. It is gas and is highly inflammable in air and poisonous Diborane is used for preparing substances such as high energy fuel and propellants.

Other Methods:

CHEMICAL PROPERTIES OF DIBORANE:

The Boranes unddergo different type of chemical reactions like oxidation, pyrolysis, Nucleophilic and electrophic  and reactions with bases such as OH- and NH3.

(1) Reaction with Na: Diborane reacts with sodium amalgum to form an addition product B2H6Na2.

(2) Reaction with air: the reaction of diborane with oxygen is highly exothermic and due to evolution of enormous amount of heat energy it can use as industrial fuel and propellants and not use as domestic due to its poisonous nature..

(3) Thermal Stability: B2H6 stable only at low temperature when heated 100 to 250 degree it changes into higher hydrides and On heating to 700ºC diborane dissociates.


Note: - Formation of B2H2Cl4 shows that the 2H left in B2H2Cl4 are responsible for dimmer formation (Bridge bond). Diborane has only four replaceable hydrogen and with their replacement, the dimeric structure continuous to be as such. Remaining  two hydrogen when they get displaced, the dimeric structure break indicating that these two hydrogen are act as bridging hydrogen.  

(9) Reaction with Ammonia (NH3):

(1) Diborane react with excess NH3 at temperature to form (inorganic graphite) Boron nitride (BN) x.while when diborane and NH3 react in 1:2 ratios at low temperature give   Inorganic Benzene (Borazole).

(2) Diborane is electron-deficient molecule and hence it reacts with several molecules having lone pair(s) of electron like CO, ether, amines, to form complex compounds.

(3) B2H6 give symmetrical cleavage with respect to only large size and weak amines CO, H¯, N(CH3)3 , THF, PH3, PF3 , OEt3 OMe2 ,Pyridine, Thiophene ,SMe2, Set3 etc.

(4) In the presence of small and strong base B2H6 undergo unsymmetrical cleavage like NH3, H2N (CH3), HN (CH3)2 etc

ILLUSTRATIVE EXAMPLE:

(10) Methylation of Doborane:

(1) In diborane two boron atoms and four terminal hydrogen atoms lie in one plane. While two bridge hydogen atoms (encircled ) lie smmetrically above and below the plane.

(2) Total valence electrons in B2H6 is 12(6 from boron 3x2) and 6 from six hydrogen atoms) and there are two B-H-B (3C-2e) bridge bonds and four B-H (2C-2e) terminal bonds.

(3) Bond energy of B-H-B bond is 441 kjpermole which greater than bond energy B-H bond (341Kjpermole) hence methylation of diborane no more than four hydrogen.



(4) In above reaction it is clearly reveal that none of the bridge hydrogen in B2H6  has been replaced by –CH3 .ie in this reaction both the bridge bond remaine undissociate.

Structure of "Inorganic Benzene" /Borazole/Borazine:

Structure of Boron Nitride:

Structure of Fulelrences:

Structure of Graphite:


PHYSICAL PROPERTIES DIBORANE:

(1) Diborane is a colourless gas with a foul smell and is extremely toxic.

(2) Melting point = -164.85oc and Boiling point = -92.59oc

(3) It is an extremely reactive inflammable gas which burns in air with a green flame

Structure of Boron nitride (Inorganic Graphite):

Diborane react with excess NH3 at temperature to form boron nitride (BN) x.while when diborane and NH3 react in 1:2 ratios at low temperature give Borazole.

Boron Nitrides exist two forms just like allotropic forms of carbon (Graphite and Diamond) and both have formula (BN)x.

(i) Boron Nitride (Inorganic Graphite):

(1) Boron nitride is a hexagonal 2D planar giant covalent network , slippery  and a white solid with a layered structure like graphite. Doe to similar structure with graphite it know as “Inorganic graphite” and due to white colour  it is also called “white graphite”

(2) The thermodynamically stable phase of boron nitride, BN, consists of planar sheets of atoms like those in graphite The planar sheets of alternating B and N atoms consist of edge shared hexagons and, as in graphite, the B-N distance within the sheet (145 pm) is much shorter than the distance between the sheets (333 pm,). The difference between the structures of graphite and boron nitride, however, lies in the register of the atoms of neighboring sheets:

(3) The B-N-B or N-B-N bond angle is 120oc . It may be expected for perfect hexagonal ring bond network just like graphite. And boron and nitrogen atoms are sp2 hybridized.

(4) Boron nitride (Inorganic graphite ) is a very good insulator (thermal and electrical) and chemically very inert , chemically posses great stability due to the  very strong B-N bonding  in the 2D layers structure. It melts under pressure at  3000oc  so it is great thermal stability.

(5) In (BN)x the hexagonal rings are stacked directly over each other, with B and N atoms alternating in successive layers; in graphite, the hexagons are staggered. Molecular orbital calculations suggest that the stacking

(6) In (BN)x stems from a partial positive charge on B and a partial negative charge on N. This charge distribution is consistent with the electronegativity difference of the two elements.

 (7)In  Boron nitride(BN)x the Vander Waals forces holding the sheet in line with each other are stronger, so boron nitride is not as good a good lubricant as graphite. However , the use of boron nitride as a lubricant is noted as high temperature due to its chemical stability.

(8) As with impure graphite, layered boron nitride is a slippery material that is used as a lubricant. Unlike graphite, however, it is a colorless electrical insulator, as there is a large energy gap between the filled and vacant π bands

Uses:

(1) Boron nitride ceramics us in high temperature (range 2700-3000oc)  equipment due to excellent thermal stability, thermal shock stability and chemical stability.

(2) Boron nitride based ceramics are stable in air at 1000oc while carbon-graphite based materials ignited at that temperature.

(3) Hexagonal boron nitride can be made in single layers and can also be formed into nanotubes. And that nanotubes are used for wire sieving and a catalyst support.

(4) Hexagonal boron nitride can be incorporated in ceramics, alloys, resins, plastics, rubbers to give them self-lubricating properties. And plastics based hexagonal boron nitride  decrease thermal expansion, increased thermal conductivity, increased electrical insulation. 

Structure of "Borazon" (Cubic boron nitride):