The standard enthalpy of formation of NH3 is– 46.0 kJmol–1. If the enthalpy of formation of H2 from its atoms is – 436 kJ mol–1 and that of N2 is – 712 kJ mol–1,the average bond enthalpy of N – H bond is NH3 is
-964 kJ mol-1
+352 kJ mol-1
+1056 kJ mol-1
+1056 kJ mol-1
Consider the reaction:
Cl2(aq) + H2S(aq) → S (s) + 2H+ (aq) + 2Cl- (aq)
The rate equation for this reaction is
I. Cl2 + H2S → H+ +Cl- + Cl+ +HS-
II. H2S ⇌ H+ + HS- (fast equilibrium)
Cl2 + HS- → 2Cl- + H+ + S (slow)
II only
Both (I) and (II)
Neither (I) nor (II)
Neither (I) nor (II)
If 10–4 dm3 of water is introduced into a 1.0 dm3 flask at 300 K, how many moles of water are in the vapour phase when equilibrium is established?(Given: Vapour pressure of H2O at 300 K is 3170 Pa; R = 8.314 J K–1 mol–1)
5.56 x 10-3 mol
1.53 x 10-2 mol
4.46 x 10-2 mol
4.46 x 10-2 mol
The energy required to break one mole of Cl— Cl bonds in Cl2 is 242 kJ mol–. The longest wavelength of light capable of breaking a single Cl — Cl bond is
(c= 3 x 108 ms–1and NA = 6.02 x 1023 mol–1)
594 nm
640 nm
700 nm
700 nm
D.
700 nm
Energy, E = NA
The ionization energy of He+ is 19.6 x 10–18 J atom–1. The energy of the first stationary state (n = 1) of Li2+ is
4.41 x 10-16 J atom–1
-4.41 x 10-17 J atom–1
-2.2 x 10-15 J atom–1.
-2.2 x 10-15 J atom–1.
Three reactions involving H2PO4- are given below
I. H3PO4 + H2O → H3O+ + H2PO4-
II. H2PO4- + H2O→ HPO42- + H3O+
III. H2PO4- + OH- → H3PO4 + O2-
In which of the above does H2PO4- act as an acid
(II) only
(I) and (II)
(III) only
(III) only
In aqueous solution the ionization constants for carbonic acid are
K1 = 4.2 x 10-7 and K2 = 4.8 x 10-11.
Select the correct statement for a saturated 0.034 M solution of the carbonic acid.
The concentration of CO32- is 0.034 M
The concentration of CO32- is greater than that of HCO3-
The concentration of H+ and HCO3- are approximately equal
The concentration of H+ and HCO3- are approximately equal
The correct sequence which shows decreasing order of the ionic radii of the elements is
Al3+ > Mg2+ > Na+ > F- > O2-
Na+ > Mg2+ > Al3+ > O2- > F-
Na+ > F- > Mg2+ > O2- > Al3+
Na+ > F- > Mg2+ > O2- > Al3+
The solubility product of silver bromide is 5.0 x 10-13. The quantity of potassium bromide (molar mass taken as 120 g mol–1)to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is
1.2 x 10-10 g
1.2 x 10-9 g
6.2 x 10-5 g
6.2 x 10-5 g