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Chemistry >> General Chemistry >> Mole Concept and Stoicheometry IIT JEE

A decapeptide (Mol.wt 796) on complete hydrolysis gives glycine(Mol.wt 75) , alanine and phenylalanine.  Glycine contributes 47 % to the total weight  of the hydrolysed products . The number of glycine units present in the decapeptide is

Asked By: NITIN RAO
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Joshi sir comment

47 % of (796+162) = 958*47/100 = 450 approx

so no of glycene units = 450/75 = 6 approx

here 162 is taken for the weight of 9 water molecules required for breaking the decapeptides.

Chemistry >> Physical Chemistry >> Electrochemistry IIT JEE

The change in standard gibbs free energy of given cell at NTP

Zn I Zn(2+) II OH- I Ag2O I Ag         Eo =1.104V

Asked By: NIKHIL VARSHNEY
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Joshi sir comment

Zn  ----->    Zn++   + 2e-

Ag2O  +  H2O + 2e-  ------>    2Ag  +  2OH-

so Gibbs free energy change = nFE = 2*96500*1.104

Chemistry >> Physical Chemistry >> Electrochemistry IIT JEE

A CURRENT OF 0.25 A  IS PASSED THROUGH 400ML OF A2.0 M SOLN OF NaCl FOR 35 MINUTES.WHAT WILL BE THE PH OF THE SOLN AFTER THE CURRENT IS SWITCHED OFF?

Asked By: NIKHIL VARSHNEY
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Joshi sir comment

q = it = 0.25*35*60 = 525 coul. 

so no. of eq.( of H2)  formed = 525/96500 = 21/3860, same will be the no. of moles

total initial no. of moles of NaCl = 2*0.4 = 0.8 moles

remaining no. of moles of H+ = 0.8 - (21/3860)

so pH = -log[H+] 

Chemistry >> Physical Chemistry >> Electrochemistry IIT JEE

N2 gas is formed by electrolysis of magnesium nitride .The volume of one equivalent of N2 gas evolved at NTP is

Asked By: NIKHIL VARSHNEY
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Joshi sir comment

Mg3N2    −−−−>     3 Mg + N2

so n factor of N = 3 , for N2 it will be 6, so one equivalent of N2 = 22.4/6 = 11.2/3         

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry IIT JEE

A compound contains 3.2% of oxygen . the minimum molecular weight of the compound is ?

Asked By: AMIT DAS
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Joshi sir comment

atomic wt. of oxygen = 16

so m.w./100 = 16/3.2 or m.w. = 500

Chemistry >> Physical Chemistry >> Chemical and Ionic Equilibrium Board Exam

what is difference between dissociatio and ionisation?

Asked By: ANUJ KUMAR YADAV
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Joshi sir comment

Dissociation is the reaction in which two or more than two product molecules are formed.

ex.                  PCl5   --->     PCl3  +  Cl2

whereas ionisation is the reaction in which ions are formed 

ex.               MgCl2  ---->    Mg++   +  2 Cl-

Chemistry >> Physical Chemistry >> Electrochemistry Others

what is kholarsh law ?

 

Asked By: VIKRANT KUMAR
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Joshi sir comment

According to the law, the total molar conductance of a solution will be the sum of ionic conductance of the anion and cation of the electolyte

for example molar condutance of NaCl solution = λNa+  +   λCl-

Chemistry >> Inorganic Chemistry >> d and f block elements IIT JEE
Lanthanide contraction
Asked By: MOHD NASEEM
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Joshi sir comment

Lanthanide contraction is based on the poor shilding effect of f orbital electrons. Due to this unexpected contraction in size on moving down in a group occurs 

Chemistry >> Inorganic Chemistry >> d and f block elements Medical Exam
tricks to solve ques of d block elements
Asked By: MOHD NASEEM
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Joshi sir comment

Periodic properties do not follow the general trend in d block so there is no short cut 

Read the complete lesson carefully in details and make a list for all the exceptions  then try the objective questions with a book having no error. At the end of every 10 days revise these notes

At the next revison you will feel more comfort .

Chemistry >> Physical Chemistry >> Electrochemistry IIT JEE

  what will be the value of molar conductance for 0.001M aqueoussolution for NH3 ? giveen  k =1.6*10-5  and  equivalent conductance=0.0238

 

Asked By: SHUBHAM VED
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Joshi sir comment

NH3 + H+(aq) = NH4+ 

0.001                   0                                 at start

0.001(1-α)          0.001α                       at eq.

now k = 0.001α / 0.001(1-α)

solve this equation for α and getconcentration of NH4+

then use the formula molar conductance = eq. conductance / concentration of NH4+

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