The radius of the second Bohr orbit for the hydrogen atom is :
(Plank's const. h = 6.6262 × 10–34 Js ; mass of electron = 9.1091 × 10–31 kg ; charge of electron
e = 1.60210 × 10–19 C ; permittivity of vacuum
∈0 = 8.854185 × 10–12 kg–1 m–3 A2)
1.65Å
4.76Å
0.529Å
0.529Å
pKa of a weak acid (HA) and pKb of a weak base (BOH) are 3.2 and 3.4, respectively. The pH of their salt (AB) solution is
7.2
6.9
7.0
7.0
The most abundant element by mass in the body of a healthy human adult are :
Oxygen (61.4%) ; Carbon (22.9%), Hydrogen(10.0%) ; and Nitrogen (2.6%). The weight which a 75 kg person would gain if all 1H atoms are replaced by 2H atoms is
15 kg
37.5 Kg
7.5 Kg
7.5 Kg
In the following reactions, ZnO is respectively acting as a/an :
(a) ZnO + Na2O → Na2ZnO2
(b) ZnO + CO2 → ZnCO3
base and acid
base and base
acid and acid
acid and acid
Given
C(grahite) + O2(g) → CO2(g)
ΔrH° = - 393.5 kJ mol-1
H2(g) + 1/2O2(g) → H2O (l)
ΔrH° = +890.3 kJ mol-1
Based on the above thermochemical equations, the value of ΔrH° at 298 K for the reaction
C(grahite) + 2H2(g) →CH4 will be
+74.8 kJ mol–1
+144.0 kJ mol–1
–74.8 kJ mol–1
–74.8 kJ mol–1
The group having isoelectronic species is
O2– , F–, Na+ , Mg2+
O– , F–, Na, Mg+
O2–, F–, Na ,Mg2+
O2–, F–, Na ,Mg2+
Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect is :
Both form basic carbonates
Both form soluble bicarbonates
Both form nitrides
Both form nitrides
Which of the following molecules is least resonance stabilized?
D.
A water sample has ppm level concentration of following anions
F-= 10; SO42- =100; NO3-= 50
the anion/anions that make/makes the water sample unsuitable for drinking is /are:
only NO3-
both 2 SO4- and NO3-
only F–
only F–