Atoms And Molecules Class 9 Chemistry Worksheet Pdf
Class 9 Chemistry students should refer to the following printable worksheet in Pdf for Atoms And Molecules in standard 9. This test paper with questions and answers for Grade 9 Chemistry will be very useful for exams and help you to score good marks
Class 9 Chemistry Worksheet for Atoms And Molecules
CBSE Class 9 Chemistry Worksheet - Atoms and molecules (2)
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Q1 What are polyatomic ions? Give examples.
Q2 Write the chemical formulae of the following compounds.
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate (d) Aluminium chloride
Q3 Calculate the molar mass of the following substances
(a) Hydrogen molecule,H2
Q4 What is the mass of
(a)1 mole of nitrogen atom
(b)4 moles of Aluminium atom
(c)10 moles of sulphuric acid
Q5 Convert into moles
(a) 12g of oxygen gas
(b) 20g of water
(c) 22g of carbon dioxide
Exam Questions NCERT Class 9 Science Chapter 3 Atoms And Molecules
Question. How does an atom exist?
Ans : Atom exists in the form of atom, molecule or ions.
Question. Define law of constant proportion.
Ans : Law of constant proportion states that, ‘In a pure chemical substance, the elements are always present in definite proportions by mass.’
Question. State the number of hydrogen atoms in 1 g of hydrogen.
Ans : One gram of hydrogen = One mole = 6.022 × 1023 atoms
Question. State the law of conservation of mass.
Ans : This law states that the mass can neither be created nor destroyed in a chemical reaction. That is ‘bass of reactants is always equal to mass of products.
Question. Who introduced the word ‘Mole’?
Ans : ‘Wilhelm Ostwald’ introduced the word ‘Mole’.
Question. What is Avogadro Constant?
Ans : The number of particles present in one mole of any substance is fixed with a value of 6.022 × 1023.
Question. What is the full form of IUPAC?
Ans : International Union of Pure and Applied Chemistry.
Question. Write atomicity of the following : (i) Sulphur, (ii) Phosphorus
Ans : (i) Polyatomic,
(ii) Tetra atomic.
Question. What is the difference between an atom and molecule?
Ans : An atom is the smallest particle of an element which may or may not have independent existence. For example : Na, Al, Fe, etc. Molecule is the smallest particle of the element or compound which can exist independently. For example : O2, H2, N2, etc. 25. Name two elements which have same atomic number. Ans : Two elements cannot have the same atomic number.
Question. What is molar mass? What are its units?
Ans : The mass of one mole of a substance is called its molar mass. Its unit is gram per mole (gmol–1).Question. Give an example in each of the following cases :
(i) a divalent anion
(ii) a trivalent cation
(iii) a mono-valent anion.
Ans : (i) O2– (ii) Fe3+ (iii) I–
Question. What is the use of mole concept?
Ans : Applications of mole concept :
(i) We can calculate the number of basic particles from the number of moles as the number of moles of a substance is directly proportional to the number of elementary particles.
(ii) One mole of gas occupies 22.4 litres at 273K.
(iii) One mole of any gas occupies the same volume at same pressure and temperature.
(iv) One mole is equal to 6.022 × 1023 atoms. So, we can calculate the absolute masses of atoms and molecules.
Question. Give the postulates of Dalton’s atomic theory.Ans : Every element is composed of extremely small particles called atoms. Atoms of a given element are identical, both in mass and properties. Different chemical elements have different kinds of atoms; in particular, their atoms have different masses.
Atoms cannot be created, destroyed or transformed into atoms of other elements. Compounds are formed when atoms of different elements combine with each 115.
Please click the below link to access CBSE Class 9 Chemistry Worksheet - Atoms and molecules (2)
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