Answer: Molecular mass; Formula unit mass; Mole; Molar mass; Class 9 Chemistry Atoms and Molecules: Atomic mass: Atomic mass. In flask Q: 1 mole of ozone gas = 6.022 x 1023 molecules agree to the. Atom is not the smallest particle as it is made up of protons, neutrons and electrons. Question 16. Name the scientist who laid the foundation of chemical sciences. (b) Write the formulae of the following compounds: (iii) O3 Only their average comes out to be in fraction in elements which exists as isotopes. For network solids, the term formula unit is used in stoichiometric calculations. ∴ Molecular formula is ZnSO11H14. Filed Under: Atoms and Molecules , Class 9 Tagged With: avogadro's number , mole , mole concept , mole of atom , mole of molecules , moles of substance , number of moles If you know the molecular weight, you know the molar mass. [NCERT Exemplar] Question 6. Calculate the number of moles for the following: [NCERT Exemplar] = 0.5 hydrogen atoms are present. What is the valency of underlined element in the following compounds? = 6.022 x 1023 Answer: of atoms of that element in the molecular formula . Define law of conservation of mass. is done on EduRev Study Group by Class 9 Students. Define atomic mass unit. A compound of carbon and sulphur has a composition of 15.8% carbon and 84.2% sulphur. (c) Calculate the molecular mass of the following: Important Questions for CBSE Class 9 Science Chapter 3 Atoms and Molecules IMPORTANT QUESTIONS 1 MARK QUESTIONS Question. M2O. (b) Find the number of atoms in 12 g of carbon. molecular weight synonyms, molecular weight pronunciation, molecular weight translation, English dictionary definition of molecular weight. molar mass of O2 molecules Question 14. Answer: Bivalent cations = Zn2+, Ca2+. No. = 6.022 x 1023 x (0.1) = 6.022 x 1022. 1 g of hydrogen combines with 10.5 g carbon Answer: ∴ 1022 atoms of sulphur weighs = \(\frac{32}{6.022 \times 10^{23}}\) x 1022 = 0.531 g. (ii) Gram molar mass of CO2 = 12 + 2 x 16 = 44 g Gram molecular mass of the oxygen is 32g. A student puts his signature with graphite pencil. Cu2+, Na+, Fe3+, Cb, SO42-, PO43- Failures of Dalton Atomic Theory are: Question 5. Write the valency of sulphur in H2S, SO2 and SO3. Answer: If the mass of carbon in the signature is 10-12 g. Calculate the number of carbon atoms in the signature. Answer: Calculate the percentage of each isotope in natural Boron. (b) Baking powder how to make molecular mass and mole concept What is the unit of mole? (Atomic masses of Gold = 197 u, silver = 108 u). Extra Questions for Class 9 Science Chapter 3 Atoms and Molecules. Molar mass of Hg and S are 200.6 g mol-1 and 32 g mol-1 respectively. Name two scientists who established the laws of chemical combination? What do you understand by a polyatomic ion? Answer: (a) 1 mole of H2SO4 = 98 How many C2H6 molecules does the sample of the gas contain? In the above formulas Rule I is followed i.e. 1 The state of being composed of atoms. Answer: No. n = 1 6.22 x 1023 is defined as the Avogadro’s constant. (b) A hydrocarbon contains 10.5 g of carbon per gram of hydrogen. What is wrong with the statement ‘1 mol of hydrogen’? = 2 oxygen atoms are present o Answer: (а) Caustic potash Question 5. A 0.24 g sample of a compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. ∴ Mass of undecomposed potassium chlorate Share 0. What are the failures of Dalton Atomic theory? = 6.022 x 1022. The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance. Avogadro’s number represents how many particles? (i) Ammonium sulphate n = \(\frac { 76 }{ 76 }\) = 1 RULE I: Cross multiply the valencies of the elements to form the formula of the respective compound. (i) Atom and molecule. Give two examples each of bivalent cations and bivalent anions. (i) 1022 atoms of sulphur b. Valence. 1 molecule of caffeine will have mass = \(\frac{194}{6.022 \times 10^{23}}\) g = 3.22 × 10-22. Question 7. The number of moles, Question 11. CISCE ICSE Class 10. Answer: = 3.011 x 1023 atoms Cation: Question 18. = Gram molecular mass (iv) 6.022 × 1023 number of N2 molecules mass from number. Find the molecular formula. (a) Find the number of gram atoms of hydrogen in it. How are they related to one mole of an atom, molecule, or ion? Answer: Write the formula of its oxide. (i) + 4 (b) Element forming tetratomic molecule: P4. Question 1. = 1.51 x 1023. EduRev is a knowledge-sharing community that depends on everyone being able to pitch in when they know something. Give one example of a polyatomic cation. (i) Potassium carbonate [NCERT Exemplar] The following questions are about one mole of sulphuric acid [H2SO4]? Questions from all the topics are covered in the solutions. For example, waterhas a molar mass of 18.0153(3) g/mol, but individual water molecules have molecular masses which range between 18.010 564 6863(15) Da ( H 2 O) and 22.027 7364(9) Da … 1 mole = 6.022 x 1023 Question 24. How many molecules of sulphur dioxide can the vessel accommodate at the same temperature and pressure? 125 = Number of neutrons. ∵ 1 mole of carbon dioxide weighs = 44 g It provides answers to the questions given in the textbook. Answer: Molecular mass; Formula unit mass; Mole; Molar mass; Class 9 Chemistry Atoms and Molecules: Writing chemical formula: Writing chemical formula. = 40 + 12 + 48 Answer: Question 9. Question bank for Class 9. Use them for better understanding of the subjects. Answer: \(\frac { 30 }{ 15 }\) = 2 Suppose percentage of isotope with atomic mass 10.01 = x Question 1. 0.4 mole of oxygen gas = 6.022 x 1023 x 0.5 molecules A sample of ethane (C2H6) gas has the same mass as 1.5 × 1020 molecules of methane (CH4). % of C = 100 – 8.696 = 91.304% 1 mole = 6.022 x 1023 number Name the compound Al2(SO4)3 and mention the ions present in it. % of boron = \(\frac { 0.096 }{ 0.24 }\) × 100 = 40% (b) (i) v 6.022 x 1023 atoms of sulphur weighs = 32 g The molecule formula is (CS2)1 = CS2. 1.6 g = 0.1 mole Answers of Define molecular mass.? (iii) FeCl3, Fe2(SO4)3, FePO4. To obtained an integral ratio, we divide by smallest number 0 ; View Full Answer Atomicity is the number of atoms present in a molecule . Answer: It is not possible to see an atom with naked eye because of its extremely small size. Answer: Antoine L. Lavoiser and Joseph L. Proust. ∴ \(\frac{10^{-12}}{12}\) mole of C will have = \(\frac{6.022 \times 10^{23}}{12}\) x 1010. The empirical formula of a compound is C2H4O. Calculate the percentage composition of the compound by weight. (c) (i) HNO3 = Mass of H + Mass of N + Mass of O No. Answer: On passing electric current, it moves towards anode. 4.28 moles of oxygen atoms. Answer: Ozone (O 3) Question 3. (b) H2S Give the formulae of the compounds formed from the following sets of elements. The Questions and [NCERT Exemplar] The valency of Ca in CaCO3 is 2+ [i.e. Answer: [Atomic mass S = 32, C = 12, O = 16 and Avogadro’s number = 6 x 1023] In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula C6H12O6. = 46 + 32 + 64 One mole of gold contains N0 atoms = 6.022 × 1023 (ii) Molecular mass and formula of unit mass. How many grams of mercury are present in 225 g of pure HgS? (ii) The symbol of sodium is written as Na and not as S. Give reason. ∴ 5 moles of each will contain the same number of atoms. Answer: N molecules. Class-9 » Science. = 2.77 × 1021. CBSE Class 9 Science Chapter 3 Atoms and Molecules Class 9. Give two examples. over here on EduRev! (i) 46 g of Na atoms (number from mass) Molecular mass - calculation: Generally we use relative atomic masses of atoms for calculating the molecular … The molecular mass gives the mass of a molecule relative to that of the 12 C atom, which is taken to have a mass of 12. = 6.022 x 1023 x 0.5 x 2 atoms = 6.022 x 1023 atoms On passing electric current, it moves towards cathode. Question 7. No. Answer: 0 ; Atomicity may be defined as the nature of molecules. Table 3.2 Raunak took 5 moles of carbon atoms in a container and Krish also took 5 moles of sodium atoms in another container of same weight. The symbol ‘u’ represents unified mass. ∴ % of isotope with atomic mass 11.01 = 80%. (b) Let the molecular formula be (CS2)n. Question 17. Given mass of sulphur = 100g. The compound is called aluminium sulphate; cation: Al3+; anion: (SO4)2-. Solution: mass = atomic mass x number of moles = 55.9 x 0.5 = 27.95 g Do yourself: Find the mass of 2.5 mole of oxygen atoms [ Mass = molecular mass x number of moles] 2. ⇒ m = Mxn = 14x 0.5 = 7 g. (iv) n = \(\frac{N}{N_{0}}\) (b) Whose container has more number of atoms? Molecular mass = n × empirical formula mass 88 = n × (2 × 12 + 4 × 1 + 16) Question 13. Answer: He took equal volumes of two different gases under similar conditions of temperature and pressure. Answer: = 1 u + 14 u + 16 u x 3 = 63 u, (ii) CH3COOH = Mass of C + Mass of H + Mass of O Mass of 1 mole of water = 18 g Write the cations and anions present (if any) in the following compounds Thus, 6.022 × 1023 molecules of caffeine have mass = 194 g 1 g of glucose will need \(\frac { 108 }{ 180 }\) g of water. (c) Lime stone This discussion on Define molecular mass.? = 12.046 × 1023. What is the difference between cation and anion? No. According to law of conservation of mass the total mass before and after the reaction remains constant. Answer: [39 + 16 + 1] = 56 g mol-1, (b) NaHCO3 (a) Atomic mass of hydrogen = 1 u, (a) Whose container is heavier? Find the molecular formula. Molecular mass is a dimensionless quantity, but it is given the unit Dalton or atomic mass unit as a means of indicating the mass is relative to 1/12th the mass of a … Also called relative molecular mass . (b) NaCl (c) H2 207 – 82 = Number of neutrons ∴ 2H = 2 × 6.023 × 1023 So the molecular mass of water, which contains two atoms of hydrogen and one atom of oxygen is Its value is 22.4 L at STP. (iv) Two atoms of hydrogen and 1 atom of oxygen forming one molecule of water. Its relative molecular mass is 88. (iii) (a) Element forming diatomic molecule: H2, O2, N2 (only one). Let molecules formula be (ZnSO11H14)n. (i) Ammonium sulphate: (NH4)2SO4 n. The sum of the atomic weights of all the atoms in a molecule. S : 32 x 3 = 96 u (a) Calculate the mass of 0.5 mole of sulphuric acid. 11.5/23 mole of Na contains = 6.022 x 1023 x 11.523 mole Question 20. Molar mass of He = 4 g Question 6. 18 g = 6.023 × 1023 atoms. (d) CCl4 (a) Compute the volume of water so consumed assuming the density of water to be 1 g cm-3. Concepts covered in The Language Of Chemistry are Balancing Simple Equations, Chemical Equation, Concept for Language of Chemistry, Concept of Atomic Mass, Concept of Hydrogen, Concept of Molecular Mass, Concept of Valency, Empirical Formula of a Compound, Naming Certain Compounds, Origin of … How many atoms of gold are present in one gram of this sample of gold? Mass of Hg in 232.6 g of HgS = 200.6 g Also refer to other worksheets for the same chapter and other subjects too. 3)A definite number of atoms,molecules or ions of a substance. Free PDF Download - Best collection of CBSE topper Notes, Important Questions, Sample papers and NCERT Solutions for CBSE Class 9 Chemistry Atoms and Molecules. The valency of the metal (M) in M2CO3 is (1+) i.e., metal exists as M+ ion. Engineering Entrance Medical Entrance Exams PG Medical MBA Entrance Exam UPSC Exams Banking Exams Law Entrance MCA Entrance Exams PHD … (Atomic masses: Na = 23, P = 31, O = 16) Question 22. (i) The numbers of atoms Atomic mass of gold = NCERT Solutions for Class 9 Science Chapter 3- Atoms and Molecules is a detailed study material prepared by experts. = 2 × 1 + 1 × 16 = 18u, (b) The molecular mass of HNO3 = the atomic mass of H + the atomic mass of N + 3 × the atomic mass of O Define molecular mass.? Answer: Define atomic mass unit. Given mass = m What is the ratio of the number of molecules in both the samples? cross multiply the valencies of the elements to form the formula of the respective compound. (d) Write the names of elements present in (i) quicklime (ii) hydrogen bromide. Answer: = 6 × 6.022 × 1023 ⇒ m = M x \(\frac{N}{N_{0}}\) = 28 x \(\frac{6.022 \times 10^{2}}{6.022 \times 10^{2}}\) (Work upto two decimal places). (c) How many atoms of oxygen are present in the given sample? 2. Also, 1 mole of caffeine molecules = 6.022 × 1023 molecules example : NH4+, PO3-4, SO2-4, etc. Therefore, Empirical formula = CH. What is its Latin name? Question 6. Sample A contains one gram molecule of oxygen molecules and Sample B contains one mole of oxygen molecules. ∴ 5 moles of C atoms = 5 x 12 g = 60 g Q3: What is the law of conservation of mass? Answer: Question 12. N = n x N0 = 0.1 x 6.022 x 1023. Answer: Question 9. No, sodium is a metal and does not exist as a single atom. The valency of an element A is 4. (i) CuCl2, CuSO4, Cu3(PO4)2 Bivalent anions = SO42-, C32-. It changes to a divalent anion [A2-]. It depicts how many times an atom of an element is heavier than one-twelth (1/12 th) the mass of one atom of carbon-12 of mass of one carbon atom. (ii) Diatomic oxygen → O2 molecule Antoine Laurent Lavoisier, by establishing two important laws of chemical combination. What does the symbol ‘u’ represent? 2 × 12 + (6 × 1) + 16 = 46 g mol-1, Question 7. Q.1 Define the atomic mass unit.#AtomsAndMolecules #NcertIntextSolution Define atomicity. 1 molecule of oxygen (O2) = 2 atoms of oxygen (c) NH3 1 mole of CH4 has 6.02 × 1023 molecules. Question 11. Answer: Answer: On heating, potassium chlorate decomposes to potassium chloride and oxygen. FREE NCERT Solutions for class 9 Science, Chapter 3 - Atoms And Molecules from NCERT Textbook (Science Ncert Solutions). From the following compounds which one has a molecular mass of 106. Answer: Atomic mass unit may be defined as : The mass of one-twelfth (1/12) of the mass of one atom of carbon taken as 12 u. Atoms and Molecules. = 2 × 23 + 1 × 32 + 4 × 16 One gram molecules is the same as one gram mole of a substance. Answer: (i) Atoms cannot exist independently but molecules can. Fill in the missing data in the Table 3.2. (a) Calculate the relative molecular mass of water (H2O). ⇒ m = M × n = 28 x 0.5 = 14 g, (ii) mass = molar mass x number of moles Answer: (b) Hydrogen and sulphur The atomic mass of natural Boron is 10.81. Answer: Question 14. How are molecular formula and empirical formula related to each other? [NCERT Exemplar] (f) Common salt. (a) Empirical formula is the chemical formula which gives us the simplest whole number ratio between the atoms of various elements present in one molecule of a compound. Question 15. It is number of atoms in exactly 12 g of carbon-12. Molar Mass of CaCO3 = Atomic mass unit of an element is one twelfth (1/12th) of the mass of one atom of carbon-12. (b) Calculate the formula unit mass of CaCO3. It states that, ‘Mass […] The element is 207 X82. (a), (b) 1 mole of CO2 has molecules (ii) Molecular mass in the sum of masses of the atoms in the molecule whereas, formula unit mass is sum of atomic masses of the atoms in its empirical formula. 1 mole of a compound = 6.023 × 1023 atoms Question 18. 76 = n x (12 + 2 x 32) of moles (n) in 1 g of gold = \(\frac { m }{ M }\) = \(\frac { 1 }{ 197 }\) Molar mass of HgS = 200.6 + 32 = 232.6 g mol-1 What happens to an element ‘A’ if its atom gains two electrons? Formula of the carbonate of a metal M is M2CO3. 1 mole of glucose needs 6 moles of water Calculation of molecular formula: (i) Two atoms of oxygen 20 Find the number of protons and neutrons in the nucleus of an atom of an element X which is represented as 207 X82. (a) CH3COONa ∴Molar mass of the element = 56 g mol-1. = 12 u x 2 + 1 u x 4 + 16 u x 2 Dalton was the first scientist to use the symbol for the name of the elements in a specific sense but it was difficult to memorise and in use, so Dalton’s symbols are not used in chemistry. (a) Cluster of atoms that acts as an ion are called polyatomic ions. Therefore, the formula of metal chloride is MCl. In class 11, you will revisit all of these.] n = \(\frac { 88 }{ 44 }\) = 2 1 molecule of methane contains (6 + 1 × 4) = 10 electrons Atom’s mass can be transformed to energy (E = mc. The formula of its oxide is A2O2 or AO2. (ii) Magnesium chloride : MgCl2. % of oxygen = \(\frac { 0.144 }{ 0.24 }\) × 100 = 60%. Then percentage of isotope with atomic mass 11.01 = 100 – x (Atomic mass of C = 12 u, O = 16 u) MNO3 is the formula of nitrate of metal M. Write the formula of its oxide. (b) Calculate the molecular mass of HNO3. Question 1. Cinnabar (HgS) is a prominent ore of mercury. of water? The molecular mass can be calculated from the chemical formula and is expressed in conventional atomic mass units equal to 1/12 of the mass of a neutral carbon-12 (12 C isotope) atom. Question 9. Molar mass of S 8 = 32 x 8 g = 256g. Answer: (ii) Calcium chloride. A gold sample contains 90% of gold and the rest copper. Find the molecular formula of the compound, assuming that all the hydrogen in the compound is present in water of crystallisation. Where do we use the words mole and mol? Write the formula of its chloride. ⇒ N = 1.5055 x 1023 Answer: (i) Atoms cannot exist independently but molecules can. (a) Write the chemical symbols of two elements: Answer. Avogadro’s numbers (N0) represents 6.022 × 1023 particles. We know that: Mass of Hg in 225 g of HgS = \(\frac { 200.6 }{ 232.6 }\) × 225 = 194.05 g. Question 2. How many grams of water would be required to produce 18 g of glucose? Its the mass of a molecule . Like O2 molecule of oxygen it contain 2 atoms of oxygen and sulphur molecule=S8 that means it contains 8 atoms of sulphur. Question 12. Jan 10,2021 - Define molecular mass.? 23 + 1 + 12 + (3 × 16) = 84 mol-1, (c) CaCO3 Empirical formula = Na3PO4. of moles = Given mass / Molar mass … Empirical formula mass = 12 x 1 + 1 x 3 = 15 1.0 g of water contain = (6.022 x 1023)/18 molecules 1 mole of C has = 6.022 x 1023 (a) Define polyatomic ions. (ii) 8 g O2 molecules (number of molecules from mass), (iii) 0.1 mole of carbon atoms (number from given moles) Question 4. Define Or Explain the Term Relative Molecular Mass . Question Papers 301. (b) NH3 Density of water = 1 g/ml, therefore 1 ml of water weighs 1 g. = 142 a.m.u. Answer: Answer: Molecular mass of the molecule: The sum of the atomic masses of all the atoms in a molecule of a substance is called the molecular mass of the molecule. 0.1 mole has 6.02 × 1022 molecules. Answer: Question 13. Answer: Question 3. For every 2 hydrogen there are oxygen atoms (e) Ethanol Molecular mass = n x empirical formula mass | EduRev Class 9 Question is disucussed on EduRev Study Group by 164 Class 9 Students. Let mass of undecomposed potassium chlorate = x g (d) SrCl2 (ii) O2 = 3.34 x 1022 molecules. Give an example of a triatomic molecule of an element. Differentiate between: What is the difference between 2H and H2? (c) Al2(SO4)3 (a) In H2SO4 → 2 gram atoms of hydrogen are present, (b) One mole of H2SO4 contains = 6.023 × 1023 molecules Molar Mass of Na2SO4 = Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolved in water. (c) 1 mole of CO2 has oxygen atoms = 2 x N0 ∴ % of isotope with atomic mass 10.01 = 20% In flask P:1 mole of oxygen gas = 6.022 x 1023 molecules Find the empirical formula of the compound. Question 5. 287 n = 287 Its calculated as the sum of the atomic weights of each constituent element multiplied by the no. After reaction, mass of potassium chloride = 14.9 g Mass of oxygen = 9.6 g Answer: (a) CH3COONa = 5.5 g, Question 15. (iii) Triatomic oxygen → O3 molecule No of moles = n Answer: Molecular formula gives us the actual number of atoms of various elements present in one molecule of a compound. (b) The relative molecular mass of the compound is 76. Question 4. Question 15. Define or explain the term. (iv) + 4, Question 8. Answer: Answer: Concise Mathematics Class 10 ICSE Solutions 2018, molecules (number of molecules from mass), CBSE Important Extra Questions for Class 11 Political Science Chapter Wise, Class 11 History Important Questions Chapter 11 Paths to Modernization, Class 11 History Important Questions Chapter 10 Displacing Indigenous Peoples, CBSE Important Extra Questions for Class 12 Accountancy Chapter Wise, Class 11 History Important Questions Chapter 9 The Industrial Revolution, Class 11 History Important Questions Chapter 8 Confrontation of Cultures, Class 11 History Important Questions Chapter 7 Changing Cultural Traditions, Class 11 History Important Questions Chapter 6 The Three Orders, Class 11 History Important Questions Chapter 5 Nomadic Empires, Class 11 History Important Questions Chapter 4 The Central Islamic Lands, Concise Mathematics Class 10 ICSE Solutions. of ions = No. (d) Caustic soda (i) Which are formed from the first letter of the elements name. 1. (d) Carbon and chlorine 15/40 mole of Ca contains = 6.022 x 1023 x 15/40 mole Question 9. ∴ 1/2 mole of H2SO4 = 49 g. (c) In H2S molecules, number of atoms = 3