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- The frequency of light emitted for the transition n = 4 to n = 2 of He+ is equal to the transition in H atom (2) n = 2 to n = 1 2
- Ionisation energy of He+ is 19.6×10-18J atom-1. The energy of the first stationary state (n = 1) of Li2+ is (3) -4.41×10⁻¹⁷ J atom^(-1 ) Given I.E = 19.6×10⁻¹⁸ I.E ∝ z² (I.E) Li²⁺/He⁺ = (9/4)×19.6×10⁻¹⁸ = -4.41×10⁻¹⁷ 1
- The energy required to break one mole of Cl–Cl bonds in Cl2 is 242 kJ mol-1. The longest wavelength of light capable (1) 494 nm We have B.E = 242KJ/Mol E = h_cN_A/λ ∴ λ = h_cN_A/E = 3×10⁸×6.626×10⁻³⁴×6.02×10²³/(242×10³) = 0.494×10⁻³×10³ = 494 nm 1
- The radius of the second Bohr orbit for the hydrogen atom is : (4) 2.12 A Radius of n^th Bohr orbit in H atom = 0.53 n²/Z For hydrogen Z = 1 Radius of 2^(nd )Bohr orbit in H atom = 0.53 ×2²/1 = 2.12 1
- Calculate the wavelength (in nanometer) associated with a proton moving at 1.0×103ms-1 (4) 0.40 nm Given m_p = 1.67×10⁻²⁷kg h = 6.63×10⁻³⁴Js v = 1.0×10³ms⁻¹ We know wavelength λ = h/mv ∴λ = 6.63×10⁻³⁴/(1.67×10^(-27 )× 1.0×10³)... 1
- if the kinetic energy of an electron is increased four times, the wavelength of the de-Broglie wave associated (2) Half Answer: The wavelength λ is inversely proportional to the square root of kinetic energy. So if KE is increased 4 times, the wavelen... 1
- What is disproportionate ? in chemistry A disproportionation reaction is one in which a species has been both oxidised and reduced (that is, the oxidation state of the related spec... 1
- Uncertainty in position of a particle of 25 g in space is 10–5 m. Hence, uncertainty in velocity (m s–1) is (Planck’s constant, h = 6.6 × 10–34 Js) Correct option is (a) 2.1 × 10^(–28) Explaination:: mass=25g=25 × 10⁻³ kg , Δx=10⁻⁵m According to Heisenberg uncertainty principle triangle... 1
- In a hydrogen atom, if the energy of an electron in the ground state is – 13.6 eV, then that in the 2nd excited state is Answer: −1.51 eV For hydrogen the energy of the n th orbit is E_n = -frac13.6n²\ eV The ground state is n = 1 , the first excited state is n... 1
- Which of the following ions has the maximum magnetic moment ? Correct option is (a) Mn²⁺ Explaination ::: number of unpaired electrons in Mn²⁺ =5 number of unpaired electrons in Fe²⁺ =4 number of unpair... 1
- Energy of H-atom in the ground state is –13.6 eV, hence energy in the second excited state is Correct answer is option (c) –1.51 eV Explaination:: 2 ^nd\ excited \ state \ n=3 E n =− 13.06/n² -By formula E₃=-13.06/3²=-13.06/9 = -1.51... 1
- Which of the following polymer is used in the manufacture of wool laminates ? The correct answer is option (1) Urea formaldehyde resin Explanation:: 1
- The green house gas/es is (are : (A) Carbon dioxide (B) Oxygen (C) Water vapour (D) Methane (1) (A), (C) and (D) only The green house gases are CO_(2 ), H₂O(vapour) & CH₄ 1
- The equivalents of ethylene diamine required to replace the neutral ligands from the coordination 2 is the correct answer for this question [Co(NH₃)₄Cl₂]Cl + 2en → [Co(en)₂Cl₂]Cl + 4NH₃ 1
- Complete combustion of 750 g of an organic compound provides 420 g of CO2 and 210 g of H2O. 3 is the answer . This is a Liebeig method for estimation of carbon and H-percentage % of H-element . 1
- A certain element crystallises in a bcc lattice of unit cell edge, length 27ºÅ. If the same element Answer: 33 Explanation:: for bcc structure 4r=sqrt3a r=sqrt3aover4 …1 For FCC structure 4r=sqrt2a r=sqrt2aover4 …2 From 1 and 2 1
- The type pollution that gets increased during the day time and in the presence of O3 is : (2) Oxidising smog In presence of ozone(O3), oxidising smog gets increased during the day time because automobiles and factories produce mai... 1
- Which of the following reaction DOES NOT involve Hoffmann bromamide degradation ? The correct answer is option 3) This reaction does not involve haffmann bromanide degradation Rest all options involve haffmann bromamide de... 1
- The process that involves the removal of sulphur from the ores is : jee main march 2021 1) roasting Removal of sulphur from the ore is done by Roasting. 1
- Which among the following pairs of Vitamins is stored in our body relatively for longer duration ? (2) Vitamin A and Vitamin D 2
- In chromatography technique, the purification of compound is independent of : Correct answer is option (2) Physical state of the pure compound In chromotography technique, the purification of a compound is independent... 1
- Which of the following is Lindlar catalyst ? (1) Cold dilute solution of KMnO4 (2) Partially deactivated palladised charcoal 2
- A group 15 element, which is a metal and forms a hydride with strongest reducing power among group 15 hydrides. The correct answer is option 2 ) Bi 2
- The gas evolved due to anaerobic degradation of vegetation causes? the correct option is a) Global warming and cancer Explanation:: The gas CH4 evolved due to anaerobic degradation of vegetation which causes... 1