Class 9 Practice Level 2 – Set 2 – Atoms and Molecules Leave a Comment / By anushka kumari / August 26, 2024 Class 9 Practice Level 2 – Set 2 – Atoms and Molecules Total questions: 25 1. A compound has an empirical formula of CH and a molar mass of 78 g/mol. What is its molecular formula? Topic: Empirical and Molecular Formulas $ \displaystyle {{{C}_{2}}{{H}_{2}}}$ $ \displaystyle {{{C}_{3}}{{H}_{3}}}$ $ \displaystyle {{{C}_{4}}{{H}_{4}}}$ $ \displaystyle {{{C}_{6}}{{H}_{6}}}$ None 2. In the reaction $ \displaystyle {{N}_{2}}+\text{ }3{{H}_{2}}\to \text{ }2N{{H}_{3}}$, , how many moles of hydrogen are required to produce 1 mole of ammonia? Topic: Chemical Reactions and Equations 1.5 moles 2 moles 3 moles 4 moles None 3. What is the product formed when magnesium reacts with hydrochloric acid? Topic: Chemical Reactions and Equations Magnesium hydroxide Magnesium chloride Magnesium carbonate Magnesium nitrate None 4. How many moles are there in 24 grams of oxygen gas ($\displaystyle {O}_{2}$)? Topic: Mole Concept 0.75 moles 1 mole 1.5 moles 2 moles None 5. What is the volume of 2 moles of nitrogen gas $ \displaystyle \left( {{{N}_{2}}} \right)$ at STP? Topic: Mole Concept 11.2 L 22.4 L 44.8 L 56.0 L None 6. How many neutrons are there in an isotope of potassium-40 (K-40) if the atomic number of potassium is 19? Topic: Atomic Structure 19 21 20 41 None 7. What is the electronic configuration of an element with atomic number 12? Topic: Atomic Structure $ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}}$ $ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{1}}}$ $ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{p}^{2}}}$ $ \displaystyle {1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}}$ None 8. Which isotope of carbon is used in radiocarbon dating? Topic: Isotopes Carbon-12 Carbon-13 Carbon-14 Carbon-15 None 9. How many protons, neutrons, and electrons are present in an atom of uranium-235 (U-235)? Topic: Isotopes 92 protons, 143 neutrons, 92 electrons 92 protons, 146 neutrons, 92 electrons 92 protons, 143 neutrons, 91 electrons 92 protons, 146 neutrons, 91 electrons None 10. What is the molecular mass of sulfuric acid? Topic: Molecular Mass and Mole Concept 96 g/mol 98 g/mol 100 g/mol 102 g/mol None 11. How many grams are there in 0.2 moles of potassium permanganate $\displaystyle \left( {KMn{{O}_{4}}} \right)$ ? Topic: Molecular Mass and Mole Concept 25.6 g 31.6 g 27.2 g 30.4 g None 12. What is the chemical formula for calcium phosphate? Topic: Chemical Formulas $ \displaystyle {CaP{{O}_{4}}}$ $\displaystyle {C{{a}_{3}}{{{\left( {P{{O}_{4}}} \right)}}_{2}}}$ $ \displaystyle C{{a}_{2}}{{\left( {P{{O}_{4}}} \right)}_{3}}$ $ \displaystyle Ca{{\left( {P{{O}_{4}}} \right)}_{2}}$ None 13. How many atoms are present in one molecule of ammonium sulphate $ \displaystyle {{{{\left( {N{{H}_{4}}} \right)}}_{2}}S{{O}_{4}}}$ ? Topic: Chemical Formulas 15 18 21 24 None 14. Which element has the highest electronegativity? Topic: Periodic Table and Elements Fluorine Oxygen Nitrogen Chlorine None 15. What is the group number of the noble gases in the periodic table? Topic: Periodic Table and Elements Group 16 Group 17 Group 18 Group 19 None 16. Which of the following statements is true about the law of conservation of mass? Topic: Basic Concepts of Atoms and Molecules Mass is neither created nor destroyed in a chemical reaction. Mass can be created but not destroyed in a chemical reaction. Mass can be destroyed but not created in a chemical reaction. Mass changes during a chemical reaction. None 17. Which subatomic particle was discovered by J.J. Thomson? Topic: Atomic Structure Proton Neutron Electron Positron None 18. An atom has 19 protons and 20 neutrons. What is its atomic number and mass number? Topic: Atomic Structure Atomic number = 19, Mass number = 39 Atomic number = 20, Mass number = 39 Atomic number = 39, Mass number = 19 Atomic number = 19, Mass number = 20 None 19. Calculate the number of atoms in 2 moles of sulphur (S). Topic: Atomic Structure $ \displaystyle 6.022\times {{10}^{{23}}}$ atoms $ \displaystyle 1.204\times {{10}^{{24}}}$ atoms $ \displaystyle 2.408\times {{10}^{{24}}}$ atoms $ \displaystyle 3.012\times {{10}^{{24}}}$ atoms None 20. In the reaction 2Na + $ \displaystyle \text{C}{{\text{l}}_{\text{2}}}$ → 2NaCl, how many grams of NaCl are produced from 46 grams of sodium? Topic: Stoichiometry 117 g 58 g 80 g 100 g None 21. How many moles of oxygen are required to completely react with 4 moles of aluminium in the reaction $ \displaystyle \text{4AI+3}{{\text{O}}_{2}}\to 2\text{A}{{\text{I}}_{\text{2}}}{{\text{O}}_{\text{3}}}?$ Topic: Stoichiometry 2 moles 3 moles 4 moles 6 moles None 22. A compound has a molecular formula $ \displaystyle {{\text{C}}_{\text{4}}}{{\text{H}}_{{\text{10}}}}\text{.}$ What is its empirical formula? Topic: Empirical and Molecular Formulas $ \displaystyle {{\text{C}}_{2}}{{\text{H}}_{5}}$ $ \displaystyle \text{C}{{\text{H}}_{3}}$ $ \displaystyle \text{C}{{\text{H}}_{2}}$ $ \displaystyle {{\text{C}}_{\text{4}}}{{\text{H}}_{{\text{10}}}}\text{.}$ None 23. In the reaction $ \displaystyle \text{Zn+}{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\to \text{ZnS}{{\text{O}}_{\text{4}}}\text{+}{{\text{H}}_{\text{2}}}$, how many grams of hydrogen gas are produced when 65 grams of zinc react completely? Topic: Chemical Reactions and Equations 2.0 g 1.0 g 4.0 g 6.0 g None 24. An atom has an atomic number of 15 and a mass number of 31. How many neutrons does it have? Topic: Atomic Number and Mass Number 15 16 31 46 None 25. Which of the following elements is located in Group 2 of the periodic table? Topic: Periodic Table and Elements Sodium Magnesium Aluminium Silicon None 1 out of 25 Time's up
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