Welcome to ChemZipper !!!: February 2019

Search This Blog


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

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


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 ?


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)?


"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?
ILLUSTRATIVE EXAMPLE (4): If uncertainty in position and momentum of electron  are equal then prove that uncertainty in velocity  is ...
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  
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. 
ILLUSTRATIVE EXAMPLE (7): An electron is accelerated by (V) volt and following graph is obtained calculate the (V) voltage?
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 .
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?
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?
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?


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


(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.  

(8) Reaction with Ammonia (NH3):
(1) 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.
(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


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

(3) It is an extremely reactive inflammable gas which burns in air with a green flame.
(4) Boranes have great affinity for water and O2 hence they do not occur in nature. Moreover borane cannot be prepared directly from its elements as they have positive enthalpy and positive free energy of formation


(1) 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.
(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) In BN, 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
(4) In BN 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.
(5) As with impure graphite, layered boron nitride is a slippery material that is used as a lubricant. Unlike graphite, however, it is a colourless electrical insulator, as there is a large energy gap between the filled and vacant π bands.
(6) In contrast to graphite, layered boron nitride is stable in air up to 1000°C, making it a useful refractory material. Layered boron nitride changes into a denser cubic phase at high pressures and temperatures (60 kbar and 2000 degree centigrade)

Top Search Topics