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66 - General Chemistry Questions Answers

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

In a hydrogen atom electron moves around the circular orbits of radii R and 4R respectively. The ratio of the time taken by them to complete one revolution is

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Joshi sir comment

mv2/r = kqe/r2

so v2α 1/r

or (r/t)2α 1/r

or t2 α r3

now solve

 

Chemistry >> General Chemistry >> Volumetric Analysis Medical Exam

The equivalent weight of N2 and NH3 for the given reaction respectively will be (if M1 and M2 are molar masses of NH3 and N2)

N2 => NH3

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Joshi sir comment

e w of N2 = 28/6

e w of NH3 = 17/3

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry Medical Exam

The density of a gas is 3.80 g/l at STP. Calculate its density at 27°C and 700 torr pressure.

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Joshi sir comment

P = dRT/M

for first condition

760 = 3.8R273/M

and 700 = dR300/M

divide and get the answer

 

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry Medical Exam

Two oxides of a metal M contain respectively 22.53% and 30.38% of O2. If the formula of first oxide is MO, the formula of second oxide is

(a) M2O3         (b) MO3         (c) M2O         (d) M2O4

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Joshi sir comment

                        M                          O

                     77.47                   22.53

m w               M                           16

formula for first oxide is MO

so 77.47/M = 22.53/16 

so M = 77.47*16/22.53 = 55

 

                    M                         O

               69.62                   30.38

m w         55                         16

so M:O = 69.62/55:30.38/16 = 1.27:1.90

1.9/1.27 = 1.5

so formula will be M2O3

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

if radius of first bohr orbit of hydrogen atom is X, then de Broglie wavelength of electron in 4 th orbit is

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Joshi sir comment

radius of fourth orbit = 16X

now put 2πr = 4λ

 

Chemistry >> General Chemistry >> Chemical Bonds Board Exam

Is there is any  relation between bond order and bond angle

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Joshi sir comment

no

Chemistry >> General Chemistry >> Chemical Bonds Medical Exam

the correct increasing order of lattice energy of the above compounds is - AlF3 , Al2O3 and AlN

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AlF3              5924 kJ/mol

Al2O3           15916 kJ/mol  

AlN               9506.8 kJ/mol

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry Medical Exam

24.5g KClO3 heated to give O2, which is allowed to react completely with H2 to form H2O. This H2 comes from Zn and H2SO4 reaction. The amount of Zn required for the purpose is

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Joshi sir comment

2KClO3 ----------------------> 2KCl + 3O2

3O2 + 6H2 --------------------> 6H2O

6Zn + 6H2SO4 -------------------> 6ZnSO4 + 6H2

so 2 mole  KClO3  -----------------------------  6 mole Zn

now solve

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry Medical Exam

If the potential energy of hydrogen electron is -3.02eV in which of the following energy levels is electron present =

1st , 2nd , 3rd  or  4th 

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Joshi sir comment

Energy = -13.6/n2 ,  Potential Energy = -27.2/n2

for n = 3 we get -3.02  

in this answer infinite is zero potential energy level

Chemistry >> General Chemistry >> Mole Concept and Stoicheometry Medical Exam

A 0.5 g sample of sodium nitrate on heating gives 44.8ml of O2 at STP. % purity of the sample is.............

my answer is 64% but the correct answer is 68%. HOW???

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Joshi sir comment

NaNO3  −−−−>    NaNO2 + 1/2 O2

molar mass of sodium nitrate = 85

so 85 gm will give 11200 ml O2

so x gm will give 11200*x/85 = 2240x/17

on comparing with 44.8

we get 2240x/17 = 44.8

so x = 44.8*17/2240 = 17/50 = 34/100 = 0.34 gm

means 0.34 gm sodium nitrate is pure in 0.5 gm. sample so % purity = 0.34*100/0.50 = 68%

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