The standard molar heat of formation of ethane ,CO2 and waterare respectively - 21.1 , - 94.1and - 68. 3 kcal .The standard molar heat ofcombustion of ethane will be :
- 372 kcal
162 kcal
- 240 kcal
183.5 kcal
A.
- 372 kcal
Combustion equation for ethane is :
C2H6 (g) +O2 (g)2CO2 (g) + 3H2O (g)= ?
= {products} - {reactants}
= {2(CO2) + 3Hf (H2O)} - {(C2H6) + 7/2(O2)}
{2 X (- 94.1) + 3 X (- 68.3)} - {(-21.1) + 7/2(O)}
={- 1888.2 - 204.9} - {-21.1}
= - 393.1 + 21.1
= - 372 kcal
Which of the following is paramagnetic ?
N2
C2
N2+
O22-
C.
N2+
C2➔ the molecular orbital configuration (12) is
➔ C2 = [(1s)2 (1s)2 (2s)2 (2s)2 (2py)2 (2pz)2]
C2 molecule is diamagnetic as it does notcontain any unpaired electron
N2➔the molecular orbital configuration (14) is
➔N2 = [(1s)2 (1s)2 (2s)2 (2s)2 (2py)2 (2pz)2 (2px)2]
N2 molecule is diamagnetic because it does notcontain any unpaired electron .
N2+➔the molecular orbital configuration (13) is
➔ N2+ = [(1s)2 (1s)2 (2s)2 (2s)2 (2py)2 (2pz)2 (2px)1]
N2+molecule is paramagnetic because it containone unpaired electron .
O22-➔the molecular orbital configuration (18) is
➔O22- = [(1s)2 (1s)2 (2s)2 (2s)2 (2px)2 (2py)2 (2pz)2 (2py)2(2pz)2]
It does not contain any unpaired electron so , it isdiamagnetic .
Intermolecular hydrogen bonding is strongest in :
C2H5OH
HF
H2O
CH3COCH3
B.
HF
Strength of H · · · · · F > H · · · · · O
NH4COONH2 (s)2NH3 (g) + CO2 (g) ,ifequlibrium pressure is 3 atm for the abovereaction .Kpfor the reaction is :
4
27
4/27
1/27
B.
27
NH2COONH4 (s)2NH3 (g) + CO2 (g)
On applying the law of mass action to thisheterogeneous system
Kp =
or Kp =X
= 32X3
= 9 X 3 = 27
Non - directional orbital is :
4p
4d
4f
3s
D.
3s
Non - directional orbital is : 3s because s - sub - shellhas only one orbital and it is spherical .Hence ,s - orbitals are non - directional .
Which of the following gas is linear ?
CO2
SO2
NO2
SO3
A.
CO2
In CO2 ,the bond length (C-O) is 1.15,hybridization of C in CO2 is sp .Thus it has alinear structure .
O=C=OO+=C-O-O--CO+ .
Which of the following is most polarised ?
Kr
He
Ar
Xe
D.
Xe
Due to increase in the atomic size of zero groupelements from He to Xe , the polarizability oftheir atom by a polar solvent increases in thesame order .Thus Xe is most polarised .
72X180zXA , Z and A are :
69 , 172
172 , 69
180 , 70
182 , 68
A.
69 , 172
When an alpha particle is ejected , results in
➔ decrease in atomic weight by four units
➔ decrease in atomic number of twoWhen a beta particle is ejected , results in
➔ no change in atomic weight
➔ increase in atomic number by one unitwhen an particle is ejected results in
➔ nochange
72X18068A17269B17269X172
A radioactive nucleus will not emit :
alpha and beta rays simultaneously
beta and gamma rays simultaneously
gamma and alpha rays
gamma rays only
D.
gamma rays only
When a radioactive nucleus are passed throughelectric or magnetic field , they are split intoradioactive rays .A radioactive substance firstemits and radiations , then it becomesunstable and emit rays .
If the Vrms is 30 R1/2 at 27oCthen calculate themolar mass of gas in kilogram .
1 Kg
2 Kg
0.001 Kg
0.002 Kg
C.
0.001 Kg
We know ,
Vrms =
=
Given Vrms = 30R1/2
T = 273 + 27 = 300 K
30R1/2 =
=
30 x 30 x R =
M =
= 1g = 0.001 kg