All questions
- 5 books and 7 pens together cost Rs 79 whereas 7 books and 5 pens together cost Rs 77, find the total cost of 1 book and 2 pens. Let the cost of a book be Rs x and that of a pen be Rs y. Then, 5x + 7y = 79 .....(i) 7x + 5y = 77 ....(iii) Multiplying equation (i) by 5 a... 1
- Shabana’s age 10 year hence will be twice as Juhi’s present age. The correct answer is shabanas age is 26 years and juhis age is 18 years Video solution::: https://youtu.be/g0836O7_m4A 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
- Identify from the following reactions the reactants that undergo oxidation and reduction A. Fe + S → FeS Here , Fe is oxidised from 0 to +2, while S is reduced from 0 to -2 Fe undergoes oxidation (as losing electrons) Sulphur und... 1
- 5. Observe the following picture a write down the chemical reaction with explanation. The picture given shows the corrosion of iron. The chemical formula of rust is Fe₂O₃.H₂O. The rust on iron does not form by a simple reactio... 1
- d. It is recommended to use air tight container for storing oil for long time It is recommended to use air tight container for storing oil for long time because, When oil comes in contact with air, it undergoes oxidati... 1
- c.While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to... 1
- b. It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly When HCl is added to Shahabad stone effervescence of CO₂ is formed. The CO₂effervescence is formed slowly with the pieces of Shahabad tiles... 1
- a.When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky i. When limestone (CaCO₃) is heated; it undergoes decomposition reaction giving calcium oxide (CaO) and carbon dioxide (CO₂) as products. ii... 1
- d. Displacement reaction 3. Explain the following terms with examples. The reaction in which the place of the ion of a less reactive element in a compound is taken by another more reactive element by formation o... 1
- c. Balanced equation 3. Explain the following terms with examples. A chemical equation in which the number of atoms of the elements in the reactant is same as the number of atoms of the elements in the produ... 1
- b. Combination reaction 3. Explain the following terms with examples. When two or more reactants combine in a reaction to form a single product, it is called a combination reaction. Example:: When HCl vapours s... 1
- There is a stream of neutrons with the kinetic energy of 0.0327 eV. The kinetic energy of neutron is displaystyle 1/2mu²=0.0327× 1.6× 10⁻¹⁹J --the unit eV is converted to J by multiplying with 1.6×10⁻¹⁹ The m... 1
- There is a stream of neutrons with a kinetic energy of 0.0327 eV. The kinetic energy of neutron is displaystyle 1/2mu²=0.0327× 1.6× 10⁻¹⁹J --the unit eV is converted to J by multiplying with 1.6×10⁻¹⁹ The m... 1
- A big dumb-bell is prepared by using a uniform rod of mass 60 g and length 20 cm. Two identical solid spheres of mass 50 g Answer: I = 46000\ mathrmg cm² = 4.6×10⁻³\ mathrmkg m² Given: rod M_r = 60\ g , L = 20\ cm ; each sphere M_s = 50\ g , R_s = 10\ cm . Distan... 1
- Convert the following decimal number into binary Answer: (a) 100110 (b) 11001.1 (c) 1010.101 For the whole-number part, divide by 2 repeatedly and read the remainders from bottom to top. Fo... 1
- A flywheel used to prepare earthenware pots is set into rotation at 100 rpm. It is in the form of a disc Given : f_(1 )= 100 rpm, f₂= 80 rpm, M =10 kg, R = 0.4m, m = 1.6kg I₁=I_(wheel )= 1/2 MR² = 1/2(10)(0.4)² ^( )= 0.8 kg m² MI of the wheel an... 1
- The road in the question 14 above is constructed as per the requirements. Given : r=72m, θ= 78°4’ , μ_s=0.8, g= 10m/s^(2 ), tanθ= tan78^(°)4’ =5 V_min =√(rg(tanθ-μ_s/1+μ_stanθ)) V_min= √(72×10(5-0.8/1+(0.8((5))) v_... 1
- A metallic ring of mass 1 kg has moment of inertia 1 kg m2 when rotating about one of its diameters The MI of the thin ring about its diameter, Ir = 1/2MR² = 1 kg\ m² Since the ring is melted and recast into a thin disc of same radius R, th... 1
- State and explain the principle of conservation of angular momentum. Use a suitable illustration. Do we use it in our daily life? When? Law (or principle) of conservation of angular momentum : The angular momentum of a body is conserved if the resultant external torque on the... 1
- Derive an expression that relates angular momentum with the angular velocity of a rigid body. Consider a rigid body rotating with a constant angular velocity w about an axis through the point O and perpendicular to the plane of the fi... 1