What is the frequency of a X-ray photon whose momentum is 1.1 x 10-23 kg-ms-2?
5 x 1016 Hz
0.5 x 1027 Hz
0.5 x 1018 Hz
5 x 1018 Hz
D.
5 x 1018 Hz
E = mc2
E = hv
mc2= hv
==
= 5 x 1018 Hz
The pH of a 0.02 M solution of HCl is :
2.2
2.0
0.3
1.7
D.
1.7
0.02 M HCl = 2 x 10-2 M HCl
[H+] = 2 x 10-2
pH = - log[H+]
= - log [2 x 10-2]
= - log 2 + 2 log 10
= - 0.3010 + 2
= 1.7
Heat of neutralisation of an acid with a base is 13. 7 kcal when :
both acid and base are weak
acid is weak and base is strong
both acid and base are strong
acid is strong and base is weak
C.
both acid and base are strong
Heat of neutralisation for strong acid and strongbase is always close to 13.7 kcal .
+H2O + AB
H = - 13.7 Kcal
The heat of neutralisation of strong acid andstrong base is actually the heat of formation of1 gmole of water from 1 g of H+ and 1 g of OH- .
Heisenberg's uncertainty principle can beexplained as :
x
x x p
x x p
p
B.
x x p
Heisenberg's uncertainty principle : It is notpossible to determine precisely both theposition and the momentum (or velocity) of asmall moving particle (e.g , electron , proton etc)
x .p
where x , p are the uncertainties with regardto position , momentum respectively .
The geometry of methane molecule is :
tetrahedral
pyramidal
octahedral
square planar
A.
tetrahedral
Methane (CH3) shows the sp3 hybridisation .So , the geometry of methane molecule is tetrahedral .
The magnitude of orbital angular momentum ofan electron of azimuthal quantum number 2 is :
B.
Orbital angular momentum =
where l = azimuthal quantum number
Hess's law is based on :
law of conservation of mass
law of conservation of energy
enthalpy is a state function
none of the above
B.
law of conservation of energy
Hess's law is based upon conservation of energy .
The heat of formarion of CO2 is - 393 kJ mol-1 .The amount of heat evolved in the formation of0.156 kg of CO2 .
- 1393 kJ
+ 1165.5 kJ
+ 1275.9 kJ
- 1165.5 kJ
A.
- 1393 kJ
Heat evolved during the formation of 44 g ofCO2= - 93kJ
Heat evolved in the formation of 0.156 kgof CO2
=
= - 1393 kJ
The bond energy is the energy required to :
dissociate one mole of the substance
dissociate bond in 1 kg of the substance
break one mole of similar bonds
break bonds in one mole of the substance
C.
break one mole of similar bonds
Bond energy :It may be defined as the energyreleased when two atoms get bonded or it isequal to the energy required to break the bondto form the neutral atoms .
e.g , H-H (g)H + H ,H = + 103 Kcal/mol
The solubility product of Mg(OH)2 at 25°C is1.4 x 10-11 .What is the solubility of Mg(OH)2in g/L ?
0.0047 g/L
0.047 g/L
0.0087 g/L
0.087 g/L
C.
0.0087 g/L
Mg(OH)2Mg2+ + 2OH-
Ksp = [Mg2+][OH-]2
1.4 X 10-11 = (s)(2s)2
1.4 X 10-11 = 4s3
s = 1.5 x 10-4 mol/L
(Mol. wt. of Mg(OH)2 = 52)
=58 X 1.5 x 10-4
= 0.0087 g/L