Class XII students were asked to prepare one litre of buffer solution of $$\mathrm{pH}8.26$$ by their Chemistry teacher: The amount of ammonium chloride to be dissolved by the student in $$0.2\mathrm{M}$$ ammonia solution to make one litre of the buffer is : (Given: $${\mathrm{pK}}_{\mathrm{b}}\left({\mathrm{NH}}_3\right)=4.74$$ Molar mass of $${\mathrm{NH}}_3=17\mathrm{g}{\mathrm{mol}}^{-1}$$ Molar mass of $${\mathrm{NH}}_4\mathrm{Cl}=53.5\mathrm{g}{\mathrm{mol}}^{-1}$$ )

The plot of $$\mathrm{pH}$$-metric titration of weak base $${\mathrm{NH}}_4\mathrm{OH}$$ vs strong acid HCl looks like :

Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R Assertion A : Permanganate titrations are not performed in presence of hydrochloric acid. Reason R : Chlorine is formed as a consequence of oxidation of hydrochloric acid. In the light of the above statements, choose the correct answer from the options given below

$$200\mathrm{mL}$$ of $$0.01\mathrm{M}\mathrm{HCl}$$ is mixed with $$400\mathrm{mL}$$ of $$0.01\mathrm{M}{\mathrm{H}}_2{\mathrm{SO}}_4$$. The $$\mathrm{pH}$$ of the mixture is _________. Given: $$\log 2=0.30,\log 3=0.48,\log 5=0.70,\log 7=0.84,\log 11=1.04$$

Which of the following statements are correct? (A) The electronic configuration of Cr is [Ar] 3d5 4s1. (B) The magnetic quantum number may have a negative value. (C) In the ground state of an atom, the orbitals are filled in order of their increasing energies. (D) The total number of nodes are given by n $$-$$ 2. Choose the most appropriate answer from the options given below :

Which of the following is the correct plot for the probability density $${\psi }^2$$ (r) as a function of distance 'r' of the electron from the nucleus for 2s orbital?

Consider the following statements : (A) The principal quantum number 'n' is a positive integer with values of 'n' = 1, 2, 3, ... (B) The azimuthal quantum number 'l' for a given 'n' (principal quantum number) can have values as 'l' = 0, 1, 2, ...... n (C) Magnetic orbital quantum number 'ml' for a particular 'l' (azimuthal quantum number) has (2l + 1) values. (D) $$\pm$$ 1/2 are the two possible orientations of electron spin. (E) For l = 5, there will be a total of 9 orbital Which of the above statements are correct?

If the radius of the 3rd Bohr's orbit of hydrogen atom is r3 and the radius of 4th Bohr's orbit is r4. Then :

The number of radial and angular nodes in 4d orbital are, respectively

The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is : [Given : The threshold frequency of platinum is 1.3 $$\times$$ 1015 s$$-$$1 and h = 6.6 $$\times$$ 10$$-$$34 J s.]

The pair, in which ions are isoelectronic with AI3+ is :

The energy of one mole of photons of radiation of wavelength 300 nm is (Given : h = 6.63 $$\times$$ 10$$-$$34 J s, NA = 6.02 $$\times$$ 1023 mol$$-$$1, c = 3 $$\times$$ 108 m s$$-$$1)

Consider the following pairs of electrons (A) (a) n = 3, $$l$$ = 1, m1 = 1, ms = + {1 \over 2} (b) n = 3, 1 = 2, m1 = 1, ms = + {1 \over 2} (B) (a) n = 3, $$l$$ = 2, m1 = $$-$$2, ms = $$-$${1 \over 2} (b) n = 3, $$l$$ = 2, m1 = $$-$$1, ms = $$-$${1 \over 2} (C) (a) n = 4, $$l$$ = 2, m1 = 2, ms = + {1 \over 2} (b) n = 3, $$l$$ = 2, m1 = 2, ms = + {1 \over 2} The pairs of electrons present in degenerate orbitals is/are :

The number of radial nodes and total number of nodes in 4p orbital respectively are :

Which of the following sets of quantum numbers is not allowed?

Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Energy of $$2\mathrm{s}$$ orbital of hydrogen atom is greater than that of $$2\mathrm{s}$$ orbital of lithium. Reason R: Energies of the orbitals in the same subshell decrease with increase in the atomic number. In the light of the above statements, choose the correct answer from the options given below.

The correct decreasing order of energy for the orbitals having, following set of quantum numbers : (A) n = 3, l = 0, m = 0 (B) n = 4, l = 0, m = 0 (C) n = 3, l = 1, m = 0 (D) n = 3, l = 2, m = 1 is :

Outermost electronic configurations of four elements A, B, C, D are given below : (A) $$3s^2$$ (B) $$3s^{2}3p^1$$ (C) $$3s^{2}3p^3$$ (D) $$3s^{2}3p^4$$ The correct order of first ionization enthalpy for them is :

Identify the incorrect statement from the following.

Given below are two statements: One is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$ Assertion $$\mathbf{A}$$ : Zero orbital overlap is an out of phase overlap. Reason $$\mathbf{R}$$ : It results due to different orientation / direction of approach of orbitals. In the light of the above statements, choose the correct answer from the options given below