Under which of the following conditions is the relation valid for a closed system ?
Constant pressure
Constant temperature
Constant temperature and pressure
Constant temperature, pressure and composition
A.
Constant pressure
At constant pressure,
The second law of thermodynamic says that in a cyclic process
work cannot be converted into heat
heat cannot be converted into work
work cannot be completely converted into heat
heat cannot be completely converted into work
D.
heat cannot be completely converted into work
Second law of thermodynamics states that in a cyclic process heat cannot be converted completely into work because attainment of 0 K temperature is impossible.
For the Paschen series the values of n1 and n2 in the expression
n1= 1, n2 = 2, 3, 4, ...
n1= 2, n2 = 3, 4, 5,...
n1= 3, n2 = 4,5,6,...
n1= 4, n2 = 5,6,7,...
C.
n1= 3, n2 = 4,5,6,...
Paschen series is the third series of hydrogen spectrum and lies in the infrared region, therefore for this series, n1 = 3 and n2 > n1,ie, 4, 5, 6,....
Which of the following will decrease the pH of a 50 mL solution of 0.01 M HCl?
Addition of 5 mL of 1 M HCl
Addition of 50 mL of 0.01 M HCl
Addition of 50 mL of 0.002 M HCl
Addition of Mg
B.
Addition of 50 mL of 0.01 M HCl
Millimoles of 50 mL of 0.01 M HCl
= 50 x 0.01 M = 0.5
pH of the solution =-log (0.5) = 0.3010
(a) On adding 5 mL of 1 M HCl,
Concentration of the resultant solution
=
:. pH of the solution = -log (0.1) = 1
(b) On adding 50 mL or 0.01 M HCl,
Concentration of the resultant solution
=
:. pH of the solution = -log (0.01) = 2
(c) On adding 50 mL of 0.002 M HCl,
concentration of the resultant solution
=
:. pH of the solution = -log (6 x 10-3)= 2.22
(d) On adding Mg,
1 mole of photon, each of frequency 2500 s-1, would have approximately a total energy of
10 erg
1 J
1 eV
1 MeV
A.
10 erg
Frequency of one photon = 2500 s-1
:. Frequency of 1 mole of photon
= 6.023 x 1023 x 2500 s-1
An organic compound made of C, H and N contains 20% nitrogen. Its molecular weight is
70
140
100
65
A.
70
Atomic mass of nitrogen= 14
Since the compound contains C, H and N, at
least one N atom must be there in the molecule.
:. The minimum molecular weight of the organic compound = 70.
Equal volumes of molar hydrochloric acid 'and sulphuric acid are neutralized by dilute NaOH solution and x kcal and y kcal of heat are liberated respectively. Which of the following is true ?
x = y
x =y/2
x = 2y
none of these
B.
x =y/2
Heat of neutralisation= Heat of formation of water (1 mol).
Hybridisation of central atom in NF3 is
sp3
sp
sp2
dsp2
A.
sp3
Number of hybrid orbitals = number of bonds + number of lone pairs
bonds + 1 lone pair = 4
.:. Hybridisation of N is sp3 and geometry of the molecule is pyramidal.
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