Author: Dr. Vikas Jasrotia

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Chemistry Class 11 Chapter 2 Question Number 2.26 and 2.27 Question 2.26: An atom of an element contains 29 electrons and 35 neutrons. Deduce (i) the number of protons and (ii) the electronic configuration of the element. Answer 2.26: (i) For an atom to be neutral, the number of protons is equal to the number of electrons. The number of protons in the atom of the given element = 29 (ii) The electronic configuration of the atom is 1s2 2s2 2p6 3s2 3p6 4s1 3d10 Question 2.27: Give the number of electrons in the species H2+,  H2, and O2+ Answer…

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Chemistry Class 11 Chapter 2 Question Number 2.24 and 2.25 Question 2.24: What is the lowest value of n that allows g orbitals to exist? Answer 2.24: For g-orbitals, l = 4. As for any value ‘n’ of the principal quantum number, the Azimuthal quantum number (l) can have a value from zero to (n – 1). For l = 4, minimum value of n = 5 Question 2.25: An electron is in one of the 3d orbitals. Give the possible values of n, l, and ml for this electron. Answer 2.25: For the 3d orbital: Principal quantum number…

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Difference Between Mixture and Compound Difference Between Mixture and Compound Mixture Compound 1. Nature: In a mixture, two or more elements or compounds are mixed, such that they do not combine chemically 1. Nature: In a compound, two or more elements unite chemically. 2. Structure: The mixture does not have a definite structure. 2. Structure: Compounds have a definite structure. 3. Composition: In the case of a mixture, their constituents can be present in any ratio, i.e., they have variable composition. 3. Compositions: In the case of a compound, the constituents are present in a fixed ratio by weight. 4.…

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Atoms and Molecules Class 9 NCERT Atoms and Molecules Class 9 NCERT Que 1. Give the unit to measure the size of an atom and give the size of the hydrogen atom. Ans 1. The unit to measure the size of an atom is a nanometre, size of the hydrogen atom is 10-10m. Que 2. What is IUPAC, give its one function? Ans 2. IUPAC is the International Union for Pure and Applied Chemistry. It gives the names of elements. Que 3. Give the Latin names for sodium, potassium, gold, and mercury. Ans 3.  Sodium → Natrium Gold → Aurum…

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Atoms and Molecules Class 9 Questions (MCQs) Atoms and Molecules Class 9 Questions Que 1. Which of the following correctly represents 360 g of water? (i) 2 moles of water (ii) 20 moles of water (iii) 6.022 × 1023 molecules of water (iv) 1.2044 × 1025 molecules of water (a) (i) (b) (i) and (iv) (c) (ii) and (iii) (d) (ii) and (iv) Que 2. Which of the following statements is not true about an atom? (a) Atoms are not able to exist independently. (b) Atoms are the basic units from which molecules and ions are formed. (c) Atoms are…

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Question 2.12: Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate the threshold frequency (ν0) and work function (W0) of the metal. https://www.youtube.com/watch?v=g26ITvZzxEI&t=10s Question 2.12: Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate the threshold frequency (ν0) and work function (W0) of the metal. Answer 2.12: Threshold wavelength of radiation (Λ0) = 6800 Å = 6800 × 10–10 m = 6.8 × 10–7m Threshold frequency (ν0) of the metal ν0 = c/Λ0 c = 3…

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Question 2.11: A 25-watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second. https://www.youtube.com/watch?v=i1KVhxl01OU&t=152s Question 2.11: A 25-watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second. Answer 2.11: Power of bulb, P = 25 Watt = 25 Js–1 The energy of one photon, E = hν = hc/Λ Substituting the values of h, c, and Λ in the above relation E = (6.626 × 10-34) (3 × 108)/0.57 × 10-6 E = 34.87 × 10–20 J Rate of emission of quanta…

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Question 2.10: Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize the sodium atom. Calculate the ionization energy of sodium in kJ mol–1. https://www.youtube.com/watch?v=fEErWcYZYYE Question 2.10: Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize the sodium atom. Calculate the ionization energy of sodium in kJ mol–1. Ans 2.10: The energy of sodium is E = Nhc/Λ Given Λ = 242 nm = 242 × 10-9 m Avogadro’s No (N) = 6.023 × 1023 Planks Constant (h) = 6.626 × 10-34 Js Velocity of light (c) = 3 × 108 m/s = 6.023 × 1023 × 6.626…

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Question 2.9: A photon of wavelength 4 × 10–7 m strikes on the metal surface, the work function of the metal is 2.13 eV. Calculate (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron (1 eV= 1.6020 × 10–19 J). https://www.youtube.com/watch?v=RFJcrhd0ius Question 2.9: A photon of wavelength 4 × 10–7 m strikes on the metal surface, the work function of the metal is 2.13 eV. Calculate (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron…

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Question 2.8: What is the number of photons of light with a wavelength of 4000 pm that provide 1 J of energy? https://www.youtube.com/watch?v=lCdbg6Dtw3I Question 2.8: What is the number of photons of light with a wavelength of 4000 pm that provide 1 J of energy? Ans 2.8: Energy (E) of a photon = hν Energy (En) of ‘n’ photons = nhν ν = c/Λ n = EnΛ /hc Where, λ = wavelength of light = 4000 pm = 4000 ×10–12 m c = velocity of light in vacuum = 3 × 108 m/s h = Planck’s constant = 6.626 ×…

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