1.An element ‘X’ forms an oxide with formula X2O3. State the valency of ‘X’ and write the formula of its chloride 2. Define mole. How many grams of sodium will have the same number of atoms as 6 grams of magnesium ? (Given Na5 23u, Mg5 24 u) 3. You are given an elements . Find out (a) Number of protons, electrons and neutrons in ‘X’ (b) Valency of ‘X’ (c) Write the chemical formula of the compound formed when ‘X’ react with (i) hydrogen, (ii) carbon 168X 4. An elements has mass number 35 and atomic number 17 find (i) the number of neutron in the element, and (ii) the number of electrons in the outermost shell. 5. Name the anion and cation which constitute the molecule of magnesium oxide 6. Percentage of three elements calcium, carbon and oxygen in a sample of calcium carbonate is given as : Calcium =40% ; Carbon =12.0% ; Oxygen = 48% If the law of constant proportion is true, what weights of these elements will be present in 1.5 g of another sample of calcium. Carbonate ? (Atomic mass of Ca = 40 u, C = 12 u, O = 16 u) 7. The description of atomic particles of two elements X and Y is given below : X Y Protons 8 8 Neutrons 8 9 Electrons 8 8 (i) What is the atomic number of Y? (ii) What is the mass number of X? (iii) What is the relation between X and Y? (iv) Which element/elements do they represent? (v) Write the electronic configuration of X? (vi) Write the cation/anion formed by the element 8. Which of the following are isotopes and which are isobars? Argon, Protium, Calcium, Deuterium. Explain why the isotopes have similar chemical properties but they differ in physical properties? 9.What is the number of molecules in 0.25 moles of oxygen ? Avogadro’s no. 6.02×10 23 . 10. Write down the formulae of (a) sodium carbonate (b) Ammonium chloride (c) Zinc oxide (d) Aluminium hydroxide11.What do the following symbols formulae stand for : (a) 2O (b) O2 (c) O3 (d) H2O (ii) Give the chemical formulae of the following compounds : (a) Potassium Carbonate (b) Calcium chloride (iii) Calculate the formulae unit mass of Al2 (SO4)3 (Given atomic mass of Al – 27u, S – 32u, O – 16u) 12. Write the chemical formula of ammonium sulphate. 13. The composition of nuclei of two atomic species X and Y are given below X Y Protons 17 17 Neutrons 18 20 Find the mass number of X and Y. State the relationship between X and Y 14. Find the mass of the following : (i) 0.5 mole of oxygen gas (ii) 3.011×10 23 atoms of oxygen (iii) 6.022×10 24 molecules of oxygen (Given atomic mass of 0=16u; No. of molecule=6.022×10 23 per mole 15. S -2 has completely filled K,L and M shells. Find its atomic number. 16. Find the number of particles in each of the following : (i) 0.1 mole of C atoms (ii) 46 g of Na atoms (Given that Na = 23u ; No. of molecule=6.022×10 23 per mole 17. Calculate the number of moles present in (i) 60g of calcium (ii) 3.011×10 23 number of oxygen atoms (Given that Ca = 40u ; Avogadro number= 6.022×10 23 ) 18. State one use each of an isotope of (i) uranium , (ii) iodine. 19. The chemical formula of oxide of an element X is X2O5. Write the chemical formula of its chloride. 20. Calculate the number of particles in each of the following : (i) 7 g of Nitrogen molecules (ii) 0.5 mole of carbon atoms (Given N=14 u ; C=12 u ; Avogadro number= 6.022×10 23 ) 21. Which of the following compounds have polyatomic ions ? NaOH, NaCl, Na2O, NaNO3 22. Sulphur dioxide (SO2) is a colourless pungent smelling gas and is a major air pollutant. (a) Write the electronic configuration of its constituent elements „sulphur and Oxygen. (Given, ). (b) Write valency of Sulphur and Oxygen. (c) Are sulphur and oxygen isotopes of same element. Explain your answer. (Given 32 S16 , 16O8) 23. What is the mass of 0.5 mole of NH3 ? Given Atomic mass of N = 14u, Atomic mass of H = 1u. (c) Calculate the number of particles in 31 g of P4molecules. Atomic mass of P=31u. ( Avogadro number= 6.022×10 23 ) (d) Find the number of moles in 87g of K2SO4 (Atomic mass of K=39u, S=32u 24. A light and a heavy object have the same momentum. What is the ratio of their kinetic energies ? Which one has a larger kinetic energy ? (ii) A ball is dropped from a height of 10m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back ? (g=10 ms -2 ) 25. Write the names of compounds represented by the following formulae : (i) KNO3 (ii) Al2(SO4)3 (iii) CCl4 (iv) H2S 26. Two boys Ram and Shyam have mass equal to 40 kg each. They start climbing a rope separately and both reach a height of 6 m. Ram takes 20 seconds and Shyam takes 25 seconds to complete the task. Who has more power? Explain your answer. (Take g =10 m/s 2 ) 27. (a) What would be the formula of chloride of ‘X’ if it is a metal and its oxide has the formula XO ? (b) Write a difference between an atom and an ion. (c) Give an example of each : (i) Triatomic molecule. (ii) Polyatomic ion. (iii) molecule of a compound (iv) cation (v) an element with valency – 3 28. In an office, a tube light of 40W, a fan of 75 W and a cooler of 150 W are installed. If the appliances are used for 8 hours per day, find the energy consumed per day in commercial unit. 29. a)Calculate the mass of 0.72 g molecule of CO2. (At mass of C=12 u, O=16 u) (b) Calculate the number of moles of iron in iron sheet containing 10 22 atoms of iron. 30. Calculate the molar mass of Nitric acid (HNO3). (Atomic Mass of H=1u, N=14u, O=16u) (b) Calculate the no. of moles in 270 g of Aluminium. (Atomic mass of Al=27 u) (c) Calculate the mass of 0.5 moles of Helium gas (Atomic mass He=4u.)
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A-1) Element X = Al ( aluminum)
Oxide of Al - Al2O3
Chloride of Al - AlCl3
A-9) Number of molecules in 0.25 moles of oxygen = 0.25 * 6.023*1023 = 1.505*1023 particles.
A-21) Out of NaOH, NaCl, Na2O, NaNO3, compound having polyatomic ion is NaNO3.