Ncert – class 9- science -Chapter 3 – Atoms and Molecules 1 Welcome to your Ncert - class 9- science -Chapter 3 – Atoms and Molecules 1 1. The average relative atomic mass of chlorine is 35.45. It consists of two naturally occurring isotopes chlorine-35 and chlorine-37. What is the fractional abundance of chlorine-37? 0.2200 0.3650 0.3550 0.4500 None 2. The number of gold atoms in 300 mg of a gold ring of 20-carat gold (Au=197: pure gold is 24 carat) is: $$7.6 \times 10^{20}$$ $$4.5\times 10^{20}$$ $$6.8 \times 10^{15}$$ $$9.5 \times 10^{20}$$ None 3. Number of atoms in 560 g of Fe (atomic mass = 56 u) is None of these Twice that of 70 g N Equal to that of 70 g N Half that of 20 g H None 4. In a chemical scale, the relative mass of the isotopic mixture of oxygen atoms \((16_{o}, 17_{o}, 18_{o})\) is assumed to be equal to 17.00 16.002 16.00 11.00 None 5. How many molecules are present in one gram of hydrogen \( H_{2} \) $$6.023\times10^{23}$$ $$3.0125\times10^{-13}$$ $$6.023\times10^{22}$$ $$3.01 \times10^{23}$$ None 6. Which of the following is a suitable example for illustrating the law of conservation of mass? (Atomic mass of O = 16 g/mol, H = 1 g/mole) 18g Of water freezes at 4 degree C to give same mass of ice. 18g of water is completely converted into vapour state on heating. 18 g of water is formed by the combination of 16 16 g oxygen with 2 g of hydrogen. 18g of water in liquid state is obtained by heating 18 g of ice. None 7. Choose the correct answer from the options given below.In water, the hydrogen-to-oxygen mass ratio is: 1:32 1:16 1:64 1:8 None 8. Which of the following cations does not form soluble complex with excess NaOH solution as well as excess NH4 OH solution ? $$Fe^{+3}$$ $$Cu^{+2}$$ $$Al^{+3}$$ None of these None 9. What is the ratio of the number of atoms of elements potassium, chlorine, and oxygen respectively present in 245g of KClO 3? 1:1:3 39:36:48 2:2:3 1:2:6 None 10. Which of the following statements is correct about the reaction given below?$$4Fe(s)+3O2(g) \rightarrow 2Fe_{2}O_{3}(g)$$ The total mass of reactants = = Total mass of the products. It follows the law of conservation of mass. Amount of Fe2O3produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess. Amount of Fe2 O3 can be increased by taking any one of the reactants (iron or oxygen) in excess. The total mass of reactants = = Total mass of the products. Therefore, the law of multiple proportions is followed. None 11. Two gaseous samples of the same compound were analyzed. One contained 1.2 g of carbon and 3.2 g of oxygen. The other contained 27.3% carbon and 72.7% of oxygen. The experimental data follows: Law of conservation of mass Law of multiple proportion Law of reciprocal proportion Law of definite proportion None 12. Which among the following is true about one mole of a gas? It always occupies 2 litres. It always occupies a fixed volume at N.T.P. It can occupy any volume at S.T.P. It always occupies 1 litre. None 13. Hydrogen combines with oxygen to form H2O in which 16 g of oxygen combine with 2 g of hydrogen. Hydrogen also combines with carbon to form CH4 in which 2 g of hydrogen combine with 6 g of carbon.If carbon and oxygen combine together then they will do show in the ratio of 1 : 2 6 : 16 12 : 24 13 : 32 None 14. On heating KClO3 at a certain temperature, it is observed that one mole of KClO3 yields one mole of O2. What is the mole fraction of KClO 4 in the final solid mixture containing only KCl and KClO 4, the latter being formed by the parallel reaction? 0.75 0.67 0.50 0.25 None 15. The average molecular mass of a mixture of gas containing nitrogen and carbon dioxide is 36. The mixture contains 280 g of nitrogen. Therefore, the amount of CO2 present in the mixture is : 44 g 4.4 g 880 g 440 g None 16. If we assume that one-sixth the mass of an atom of (\12_{C}\) isotope is taken as the reference, the mass of one molecule of oxygen will: be half its original value increase by four fold be the same be double its original value None 17. Of two oxides of iron, the first contained 2222% and the second contained 3030% of oxygen by weight. The ratio of weights of iron in the two oxides that combine with the same weight of oxygen is 1:2 1:1 2:1 3:2 None 18. A charged particle formed by the loss or gain of electrons during a compound formation is called an ..... Anion ion Positron Cation None 19. Which of the following substance is made up of only one type of particle? compound mixture element mixed metal None 20. 1.375 g of cupric oxide was reduced by heating in a current of hydrogen and the weight of copper obtained was 1.0981.098 g. In another experiment, 1.1561.156 g of copper was dissolved in nitric acid and the resulting solution was evaporated to dryness. The residue of copper nitrate when strongly heated was converted into 1.44761.4476 g of cupric oxide. State the law illustrated by these chemical combinations. Law of reciprocal proportion Law of constant composition None of these Law of multiple proportion None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
