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pH of a saturated solution of Ba(OH)2 is 12. The value of solubility product Ksp of Ba(OH)2 is
3.3 x 10-7
5.0 x 10-7
4.0 x 10-6
5.0 x 10-6
B.
5.0 x 10-7
Given, pH of Ba(OH)2 = 12
pOH = 14-pH
= 14-12 = 2
We know that,
pOH = -log [OH-]
2 =-log [OH-]
[OH-] = antilog (-2)
[OH-] = 1 x 10-2
Ba(OH)2dissolves in water as 
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Maximum number of electrons in a subshell with l =3 and n=4 is
14
16
10
12
A.
14
n represents the main energy level and l represents the subshell.
If n=4 and l = 3, the subshell is 4f.
If f subshell, there are 7 orbitals and each orbital can accommodate a maximum number of electrons, so, maximum number of electrons in 4f subshell = 7 x 2 = 14
In which of the following reactions, standard reaction entropy changes (ΔSo) is positive and standard Gibb's energy change (ΔGo) decreases sharply with increasing temperature?
C (graphite) +1/2 O2 (g) → CO (g)
CO (g) +1/2 (g) → CO2 (g)
Mg(s) +1/2O2 (g) → MgO (s)
1/2 C (graphite) +1/2 O2 (g) → 1/2 CO2 (g)
A.
C (graphite) +1/2 O2 (g) → CO (g)
Among the given reactions only in te case of
C (graphite) +1/2 O2 (g) → CO (g)
entropy increases because randomness (disorder) increases. Thus, standard entropy change (ΔSo) is positive.
Moreover, it is a combustion reaction and all the combustion reactions are generally exothermic, ie. ΔHo=-ve
We know that
ΔGo = ΔHo-TΔSo
ΔGo = -ve-T(+ve)
Thus, as the temperature increases, the value of ΔGo decreases.
Equimolar solutions of the following substances were prepared separately, which one of these will record the highest pH value?
BaCl2
AlCl3
LiCl
BeCl2
A.
BaCl2
BaCl2 is a salt of strong acid HCl and strong base Ba(OH)2. So, its aqueous solution is neutral with pH 7. All other salts give acidic solution due to cationic hydrolysis, so their pH is less than 7. Thus, pH value is highest for the solution of BaCl2.
50 mL of each gas A and of gas B takes 150 and 200 s respectively for effusing through a pin hole under the similar conditions. If molecular mass of gas B is 36, the molecular mass of gas A will be
96
128
20.2
64
C.
20.2
Given,
VA =VB = 50 mL
TA = 150 s
TB = 200 s
MB = 36
MA = ?
From Graham's law of effusion
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