Science Atoms and Molecules Class 9th

Atoms and Molecules

(Q.1)  Write down the formulae of aluminium sulphate and ethanol.

(Q.2)  144 grams of pure water is decomposed by passing electricity. 16 grams of hydrogen and 128 grams of oxygen are obtained. Which chemical law is illustrated by this statement?

(Q.3)  What is the atomicity of – (a) Ozone (b) Nitrogen (c) Neon (d) Sulphur

(Q.4)  What name is given to the number 6.023 x 1023?

(Q.5)  Select the correct statement and choose the answer from the code given below- I. Gram molecular mass of a substance contains 6.022X1023molecules. II. The molar mass of a substance is the mass of 1 mole of that substance. III. Gram molecular mass of H2O is 1. IV. The molar mass of nitrogen molecule is 28g/mol

(a) I and III     (b) I, II and IV                       (c) Only II       (d) All of these
 

(Q.6)  Which of the following are ionic compounds? (i) NH4+ (ii) CaCl2 (iii) C6H6 (iv) Al2O3

(a) (i) and (ii)               (b) (ii) and (iv)            (c) (i) and (iii)              (d) None of the above
 

(Q.7)  Select the correct statement and choose the answer from the code given below (i) All metals form cations by gaining electrons (ii) All metals form cations by losing electrons (iii) Hydrogen is a non metal but forms a cation (iv) All nonmetals form anions

(a) (ii) only      (b) (iii) and (iv)           (c) (i) and (iii)              (d) (ii), (iii) and (iv)
 

(Q.8)  An atom is made up of negatively charged electrons and positively charged protons, still it is electrically neutral. The reason is

(a) The electrons and protons are equal in number so no net charge is present.
(b) The neutrons neutralize the charge and make the atom neutral
(c) The charge on the atom is too small to be detected
(d) Both (1) and (2)
 

(Q.9)  When calcium metal (Ca) changes to calcium ion (Ca+2) the number of electron, proton and neutron

(a) Remains same
(b) Number of neutrons remains the same while the number of both protons and electrons changes.
(c) Number of neutrons and protons remains same while the number of electrons decreases by 2.
(d) Number of neutrons and electrons remains the same while number of protons increases by 2
 

(Q.11)  Select the correct statement and choose the answer from the code given below I.One mole of all substances in gaseous state contains equal number of particles (6.022X1023) and occupy equal volume (22.4 L) at STP. II.One mole of all substances contains equal number of particles (6.022X1023) at all temperatures and pressure. III.Avogadro number is equal to 6.022X1023 particles (atoms, molecules,ions). IV.One mole of N2 does not contain same number of molecules as in one mole of H2.

(a) I and IV     (b) I and III    (c) I, III and IV          (d) None of these
  

(Q.13)  The number of atoms present in 0.4 mole of Calcium (Ca) are

(a) 2.408 X 10²³             (b) 24.08 X 10²³             (c) 2.408 X 10²⁴              (d) 6.022 X 10²³
 

(Q.14)  An element A forms an oxide A2O3, the valency of A is

(a) 2     (b) 3    (c) 5     (d) 1
 

(Q.15)  Formula mass of ammonium sulphate (NH4)2SO4 is

(a) 114u           (b) 132u          (c) 120u           (d) 132u
 

(Q.16)  The chemical formula of Phosphorus and Sulphur are respectively:

(a) P₄ and S     (b) P₃ and S₈    (c) P₄ and S₈     (d) P₄ and S₆
 

(Q.17)  Which of the following gases can exist in atomic form?

(a) Oxygen (O)           (b) Neon (Ne) (c) Hydrogen (H)        (d) Nitrogen(N)
 

(Q.18)  Law of Constant Proportions was given by

(a) Newton      (b) Rutherford            (c) Lavoisier    (d) Proust
 

(Q.19)  5g of Calcium (Ca) contains [Atomic mass of Ca = 40u]
(a) 1/8mol        (b) 1/7 mol      (c) 1/8g/mol     (d) 1/9mol  (Q.20)  1 mole of NH3 molecules contains

(a) 6.022X10²³NH₃ molecules            (b) 6.022X10²² NH₃ atoms
(c) 6.022X10²³ NH₃ atoms                  (d) 6.022X10²² NH₃ molecules
 

(Q.21)  Unit of molar mass is:

(a) gm/molecule          (b) gm             (c) Moles         (d) gm/mol
 

(Q.22)  Valencies of iron are:

(a) 2 and 3       (b) 1    (c) 1 and4        (d) 4
 

(Q.23)  Cuprous sulphide is the chemical name of:

(a) CuS            (b) Cu₂S          (c) CuS₂              (d) Cu₃S
 

(Q.24)  Cation is formed due to

(a) Gain of electrons   (b) Loss of protons     (c) Loss of electrons    (d) Gain of protons
 

(Q.25)  An ionic compound is made up of:

(a) Metal-Nonmetal    (b) Cation-Cation        (c) Anion-Anion          (d) Metal-Metal
 

(Q.26)  The atomicity of noble gases is

(a) Mono-atomic         (b) Octa-atomic           (c) Tri-atomic  (d) Tetra-atomic
 

(Q.27)  What is the full form of IUPAC?

(a) Indian Union of Pure and Applied Chemistry      (b) International Union of Pure and Applied Chemistry
(c) span>Indian Union of Perfectand Applied Chemistry     (d) InternalUnion of Pure and Applied Chemistry
 

(Q.28)  When 100g of CaCO3is heated, it decomposes to yield 56g of CaO and 44g of CO2 . Which law of chemical combination is confirmed by the above statement?

(a) Law of conservation of mass                    (b) Law of multiple proportion
(c) Law of constant proportion                       (d) Avogadro's law
 

(Q.29)  Which of the following statement is correct?

(a) Maharishi Kanad proposed the term Atom           (b) Kanad said Atom could be further divided
(c) Dalton proposed the term Atom                            (d) J. J. Thomson discovered neutron.
 

(Q.30)  Which are called the building blocks of matter?

(Q.31)  Write the chemical symbols of – (a) Silver (b) Potassium (c) Tin (d) Mercury

(Q.32)  How many metres are there in 1 nanometer (nm)?

(Q.33)  Define atomicity.

(Q.34)  Atomicities of phosphorus and ozone are respectively:

(a) 4, 3             (b) 2, 2                        (c) 2, 3             (d) 4, 2
 

(Q.35)  What do we call those particles which have- (a) Less electrons than the normal atoms. (b) More electrons than the normal atoms.
(Q.36)  Which subatomic particle was not present in Thomson’s model of the atom?

(Q.37)  Mass of 0.5 M of oxygen atom is:

(a) 16 g            (b) 32 g           (c) 4 g              (d) 8 g
 

(Q.38)  Ratio of nitrogen and hydrogen in ammonia (NH3) by mass is:

(a) 3 : 1            (b) 1 : 3           (c) 3 :14           (d) 14 : 3
 

(Q.39)  Charge on phosphate ion is:

(a) -1               (b) -2               (c) -3                (d) +2
 

(Q.40)  The formula of aluminium hydroxide is

(a) Al(OH)_3.     (b) Al₂(OH)_3.   (c) Al(OH)_2.      (d) Al₄(OH)_3.
 

(Q.41)  The building block of all matters is called

(a) an ion.        (b) an atom.     (c) a molecule. (d) a compound.
 

(Q.42)  “Matter is neither created nor destroyed in a chemical reaction”. This law is known as

(a) law of multiple proportion.            (b) law of conservation of mass.
(c) law of constant proportion            (d) law of reciprocal proportion.
 

(Q.43)  An element X forms an oxide X2O3. The valency of the element X is

(a) 2.    (b) 3.   (c) 4.    (d) 6.
 

(Q.44)  A group of particles (atoms, molecules or ions) of a substance is called

(a) a mole.       (b) a molecule.            (c) a compound.          (d) an ion.
 

(Q.45)  The law of chemical combination given by Proust in 1779 is

(a) law of conservation of mass.                     (b) law of constant proportion.
(c) law multiple proportion.                            (d) law of reciprocal proportion.
 

(Q.46)  The standard for atomic scale is

(a) carbon-12.              (b) carbon-14. (c) sodium-23. (d) sodium-24.
 

(Q.47)  The molecular mass of the oxygen molecule (O2) is

(a) 8 g. (b) 16 g.          (c) 32 g.           (d) 64 g.
 

(Q.48)  C2H6 has amolar mass equal to

(a) 30 gm.        (b) 32 gm.       (c) 36 gm.        (d) 40 gm.
 

(Q.49)  The simplest combination of ions that produces an electrically neutral unit, is called

(a) a formula unit.       (b) a molecular unit.    (c) a cationic unit.       (d) an anionic unit.
 

(Q.50)  An element X forms an oxide XO3. The valency of element X is

(a) 2.    (b) 4.   (c) 6.    (d) 8.
 

(Q.51)  Aluminium ion is

(a) monovalent.           (b) divalent.    (c) trivalent.     (d) tetravalent.
 

(Q.52)  The mass of 0.2 mole of oxygen atoms is

(a) 3.2 gm.       (b) 5.2 gm.      (c) 8 gm.          (d) 16 gm.
 

(Q.53)  An element A is tetravalent and another element B is divalent. The formula of the compound formed by these elements is

(a) A₂B.           (b) AB.                        (c) A₂B_3.             (d) AB_2.
 

(Q.54)  The chloride of a metal has the formula MCl3. The formula of its phosphate will be

(a) M₂PO_4.         (b) MPO_4.          (c) M₃PO_4.         (d) M(PO₄)_2.
 

(Q.55)  The elements present in molecules of water is

(a) Hydrogen and carbon.       (b) Oxygen and Hydrogen.    (c) Oxygen and Carbon.         (d) Hydrogen and Nitrogen.
 

(Q.56)  The number of molecules of Sulphur (S8) present in 16 gm of solid sulphur is

(a) 1.022 x 10^22.              (b) 3.011 x 10^22.             (c) 3.76 x 10^22. (d) 6.023 x 10^23.
 

(Q.57)  The name of compound represented by the formula K2SO4, is

(a) di potassium sulphur tetraoxide.   (b) potassium sulphite.
(c) potassium sulphate.                                    (d) potassium sulphur oxide.
 

(Q.58)  The formula of Sodium oxide is

(a) NaO.          (b) NaO_2.           (c) Na₂O.         (d) Na₂O_2.
 

(Q.59)  Cluster of some atoms act as ion and these clusters are called

(a) compound.             (b) Mixture.     (c) polyatomic ions.     (d) mono atomic ions.
 

(Q.60)  The molecular mass of sulphuric acid is

(a) 78.  (b) 86. (c) 92.  (d) 98.
 

(Q.61)  The mass of 0.2 moles of nitrogen atoms is

(a) 1.8 gm.       (b) 2.8 gm.      (c) 3.8 gm.       (d) 4.8 gm.
 

(Q.62)  The number of aluminium ions present is 0.61 gm of aluminium oxide is

(a) 6.022 x 10²¹_.              (b) 6.022 x 10^22.             (c) 6.022 x 10²³_.              (d) 6.022 x 10²⁴_.

(Q.63)  A chlorine molecule is

(a) mono atomic.         (b) di atomic.              (c) tri atomic.               (d) poly atomic.
 

(Q.64)  The formula of aluminium sulphate is

(a) AlSO_4.          (b) Al₂SO_4.        (c) Al₂(SO₄)_3.   (d) Al₃ (SO₄)_2.
 

(Q.65)  The mass of 0.5 mole of water molecule is

(a) 4.5 gm.       (b) 9 gm.         (c) 27gm.         (d) 36 gm.
 

(Q.66)  The formula of magnesium nitride is

(a) MgN.         (b) MgN_2.          (c) Mg₃N.        (d) Mg₃N_2.
 

(Q.67)  The molar mass of a phosphorus molecule is

(a) 31 gm/mol. (b) 35 gm/mol.            (c) 98 gm/mol.             (d) 124 gm/mol.
 

(Q.68)  The formula of calcium carbonate is

(a) CaCO_2.        (b) CaC_2.            (c) CaCO_3.         (d) Ca(CO₃)_2.
 

(Q.69)  The ions present in potassium sulphate are

(a) .       (b) .     (c) .        (d) .
 

(Q.70)  The molecular mass of Sodium Chloride is

(a) 28.5 gm/mol.          (b) 35.5 gm/ mol.        (c) 43.5 gm/mol.          (d) 58.5 gm/mol.
 

(Q.71)  An element E has a valency of 4, the formula for its sulphide is

(a) ES₄.            (b) E₂S₄.          (c) ES₂.            (d) E₂S.
 

(Q.72)  The constituting elements of sulphuric acid is

(a) Sulphur and Oxygen.                                (b) Sulphur and Hydrogen.                                                          (c) Hydrogen, Oxygen and Sulphur                     (d) Hydrogen, sulphurand nitrogen.
 

(Q.73)  The mass of 0.5 mole of sugar is

(a) 90 gm.        (b) 171 gm.     (c) 180 gm.      (d) 342 gm.
 

(Q.74)  The molecular mass of Acetic Acid (CH3COOH) is

(a) 46g.            (b) 48g.           (c) 60g.            (d) 68g.
 

(Q.75)  The valencies of Aluminium ion and sulphate ion in aluminium sulphate is

(a) +2 and -3   .           (b) +3 and -2.  (c) +3 and -4.              (d) +3 and -3.
 

(Q.76)  The chemical symbol for silver is

(a) Si.  (b) Au.            (c) Ag. (d) Sr.
 

(Q.77)  The number of water molecules contained in a drop of water weighing 0.9 gm is

(a) 3.011 x 10^23.              (b) 3.011 x 10^22.             (c) 6.022 x 10²²               (d) 6.022 x 10²³
 

(Q.78)  The molecular mass of zinc nitrate is

(a) 187.4 gm/mol         (b) 189.4 gm/mol        (c) 194.3 gm/mol         (d) 196.4 gm/mol
 

(Q.79)  The mass of 0.55 mol of Hydrogen Sulphide (H2S) is

(a) 4.8 gram.(b) 5.0 gram.       (c) 5.1 gram.    (d) 5.7 gram.
 

(Q.80)  The number of moles of helium atoms present in 9.033 x 1024 atoms of Helium is

(a) 11.3 moles.            (b) 13.0 moles.            (c) 14.2 moles. (d) 15.0 moles.
 

(Q.81)  The formula of Aluminium Nitride is

(a) Al₂N₃.        (b) AlN.          (c) Al₃N₂            (d) Al₃N₃
 

(Q.82)  The number of atoms in 0.8 moles of Sodium (Na) is

(a) 2.91 10²³ atoms    (b) 3.91 10²³ atoms   (c) 4.81 10²³ atoms    (d) 5.71 10²³ atoms
 

(Q.83)  The molecular mass of Sodium bicarbonate is

(a) 64 gm.        (b) 72 gm.       (c) 76 gm.        (d) 84 gm.
 

(Q.84)  17 gm of H2O2 contains

(a) 0.50 mole of H₂O₂.            (b) 0.75 mole of H₂O₂.            (c) 1.00 mole of H₂O₂.            (d) 1.5 mole of H₂O₂.
 

(Q.85)  Write the symbols of the following elements : a. Sodium b. Calcium c. Gold d. Iron

( 2 Marks )

(Q.86)  What do you mean by Molar Mass ?

( 2 Marks )

(Q.87)  What is atomic mass unit ?

( 2 Marks )

(Q.88)   What is the law of conservation of mass?

( 2 Marks )

(Q.89)  What are molecules ?

( 2 Marks )

(Q.90)  What is an atom ?

( 2 Marks )

(Q.91)  What precentage of nitrogenis present in aluminium nitride? (Al = 27, N = 14)?

( 2 Marks )

(Q.92)  Atoms are not always combined in simple whole number ratio to form molecules. Give one example.

( 2 Marks )

(Q.93)  Write the formula of the following compound and name the elements present in them. (a) Ammonia (b) Sulphur dioxide (c) Ethanol (d) Methane

( 2 Marks )

(Q.94)  What is the mass of 5 moles of aluminium atoms?(Atomic mass of Al = 27 u)

( 2 Marks )

(Q.95)  How many times is a proton heavier than an electron? Write the absolute mass of a proton.

( 2 Marks )

(Q.96)  Which of the following are isotopes and which are isobars? Calcium, Protium, Argon, Deuterium

( 2 Marks )

(Q.97)  Calculate the number of molecules in a drop of water weighing 0.75 g. (H = 1, O = 16).

( 3 Marks )

(Q.98)  What weight in grams is represented by (a) 2 mole of CO2 (b) 5 mole of NH3.

( 3 Marks )

(Q.99)  Define ion. Distinguish between an atom and its ion.

( 3 Marks )

(Q.100)  What do you understand by Formula Unit Mass? Calculate the formula unit masses of K2CO3 and ZnO.(Atomic masses of Zn = 65u, K=39u, C=12u)

( 3 Marks )

(Q.101)  Calculate the number of moles for the following: (a)12.046 * 1023 number of He atoms (b)56g of He

( 3 Marks )

(Q.102)  An element X has a valency of 4 (a) What will be the formula of its chloride ? (b) What will be the formula of its sulphide ?

( 3 Marks )

(Q.103)  Calculate the mass of 3.011 X 1024 molecules of nitrogen gas. (Atomic mass of N=14 u)

( 3 Marks )

(Q.104)  Distinguish between the molecule of an element and the molecule of a compound?

( 3 Marks )

(Q.105)  Calculate the number of atoms of each type in 2.65 g of Na2CO3.

( 5 Marks )