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Chemistry >> General Chemistry >> Atoms and molecules Medical Exam

the frequency of radiation emitted when the electron falls n=4 to n=1 in a hydrogen atom will be (given ionisation energy of H =2.18*I0-18 J/atom )

ans=3.08*1015

Asked By: SHIVANI MALIK
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Joshi sir comment

for n = 1                      E = 2.18*10-18

for n = 4                      E = 2.18*10-18/16

so hν = 15*2.18*10-18/16

so ν = 15*2.18*10-18/16*6.634*10-34

so ν = 3.08*1015

Chemistry >> General Chemistry >> Chemical Bonds Medical Exam

which of the following has highest energy?

1)S-S

2)O-O

3)Se-Se

4)Te-Te

Asked By: SHIVANI MALIK
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Joshi sir comment

O-O         498.36 kJ/mole

S-S         425.30 kJ/mole

Se-Se      332.6 kJ/mole

Te-Te      259.8 kJ/mole

Chemistry >> General Chemistry >> Chemical Bonds Medical Exam

which of the following has zero dipole moment?  and how?

1)1-butane

2)2-methyl, 1-propyl

3)cis 2-butane

4)trans 2-butane

Asked By: SHIVANI MALIK
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Joshi sir comment

i think it should be trans 2 butene 

Chemistry >> General Chemistry >> Chemical Bonds Medical Exam

1-what is the hybridisation of s and p in s8 and P4 respectively?

 

Asked By: SHWETA BHARDWAJ
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Joshi sir comment

sp3 both

Chemistry >> General Chemistry >> Chemical Bonds Medical Exam

THE STRUCTURE OF HYDROGEN PEROXIDE IS NON-PLANER.HOW?

Asked By: SHIVANI MALIK
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Joshi sir comment

The structure of HYDROGEN PEROXIDE is like an open book. O-O bond is present in the joint and both H atom on the opposite side. Hybridisation will be sp3 for all bonds 

Chemistry >> General Chemistry >> Atoms and molecules IIT JEE

A mixture of FeO and Fe304 when heated in air to constant weight gains 5% in its weight. The % of FeO in the sample

Asked By: AMIT DAS
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Joshi sir comment

let FeO = x gm and FeO+Fe2O3= y gm so FeO = [72/(72+160)]*y and Fe2O3 = [160/(160+72)]*y

2FeO + 1/2O2  ---------->  Fe2O3

so amount of Fe2O3 formed by x gm FeO  = 160x/144

similarly amount of Fe2O3 formed by  [72/(72+160)]*y gm FeO = 160 [72/(72+160)]*y/144

so total Fe2O3 = 160x/144 + 160 [72/(72+160)]*y/144 +  [160/(160+72)]*y = 160x/144 + [160*72/232]y/144 + 160y/232

now according to the given condition {[160x/144 + [160*72/232]y/144 + 160y/232}/{x+y) = 105/100

now solve

Chemistry >> General Chemistry >> Kinetic Theory of Gases Medical Exam

What is the volume of a gas at NTP and STP ?wink

Asked By: AVANTIKA PURI
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Joshi sir comment

question is irrelevant, amount of gas is not given

Chemistry >> General Chemistry >> Kinetic Theory of Gases Medical Exam

cheeky THE CONSTANT a  IN VAN DER WALL'S EQN IS MAXM IN

A) He

B) NH3

C) CO2

D) N2

Asked By: SARIKA
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Joshi sir comment

 

Carbon dioxide                   a = 3.640

 

Helium                               a = 0.03457

 

Nitrogen                             a = 1.408

 

Ammonia                           a = 4.225

more ideal gases has lower values of a

 

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

Sir the formula for converting volume in STP condition is given in my book if volume is not given in STP condition. But my problem is that I don't know how to use it . please explain me this formula and I request you to give me Ques. related to this formula.

Asked By: HEMA RANI
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Joshi sir comment

Formula for converting volume at temperature T to STP is

P1V1/T1 = P2V2/T2

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

Two oxides of a metal contain 72.4% and 70% of metal respectively. If formula of 2nd oxide is M2O3, find that of the first?    

Sir the   answer is M3O4. But I don't know the steps for doing this type of question, so pls explain me each step!!! 

Asked By: HEMA RANI
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Joshi sir comment

for second oxide ratio of metal and oxygen = 70:30

let molcular mass of metal = M so 70/30 = 2M/3*16 

or 7/3 = 2M/48 so M = 24*7/3 = 56

now for first oxide ratio of metal and oxygen = 72.4/27.6     (By weight)

so ratio by no. of atoms = (72.4/56)/(27.6/16) = 72.4*16/27.6*56 = 1158.4/1545.6 = 3/4

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