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 (1)
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Atoms and molecules
Q1)Calculate the % of Nitrogen in urea(NH2CONH2).
Q2)Law of conservation of mass was discovered by
(a) Dalton (b) Proust (c) Lavosier (d) Richter
Q3)Two elements X&Y combine in a gaseous state to form XY in the ratio of 1: 35.5
by mass. The mass of Y which combines with 2gram of X will be
(a) 7.1 gram (b) 3.55 gram (c) 35.5 gram (d) 71 gram
Q4) Match the following:-
Column I Column II
1 . Sodium a. Yellow in colour
2 . Helium b. Diatomic
3. Sulphur c . Soft metal
4. Hydrogen d. Noble gas
Q 5 )Give one word for the following:-
(a) Metal present in haemoglobin.
(b) Reddish brown metal used in making electrical wires.
Q 6) Write correct formulae using given ions.
SO4 2- Cl- PO4
3- O2- CO3 2- OH- S2-
Q 7) What happens when : --
(a) Solution of sodium chloride and silver nitrate are mixed together.
(b) Solution of barium chloride and sodium sulphate react together.
Q8) Calculate the molecular mass of CuSO4.5H2O
[ Cu=63.5 u,S=32 u,O=16 u,H=1 u.]
Q9) The % of three elements calcium, carbon & oxygen in a sample of calcium carbonate is given as:--
Exam Questions NCERT Class 9 Science Chapter 3 Atoms And Molecules
Question. What are ionic compounds?
Ans : Ionic compounds are charged particles. Such compounds form by joining or losing or sharing the electron.
For example : Sodium chloride is an ionic compound. Its constituent particles are positively charged sodium ion (Na+) and negatively charged chloride ion (Cl–).
52. What did Antoine L. Lavoisier observe regarding the formation of compound?
Ans : He noted that many compounds were composed of two or more elements. Each compound had the same elements in the same proportions.
Question. Define one mole, give its relationship with Avogadro constant.
Ans : One mole of any species (atoms, molecules, ions or particles) is that quantity in number having a mass equal to its atomic or molecular mass in grams. The number of particles (atoms, molecules or ions) present in 1 mole of any substance is fixed, with a value of 6.022 × 1023. This number is called Avogadro constant or Avogadro number.
Question. Who stated the Law of Constant Proportion?
Ans : Joseph Louis Proust stated the Law of Constant Proportion.
Question. Name any two monatomic atoms.
Ans : Sodium, Aluminium.
Question. Write the value of charge of electron.
Ans : 1.6 × 10–19 coulomb.
Question. Name the element which is used as the reference for atomic mass.
Ans : Carbon.
Question. What are polyatomic ions? Give two examples.
Ans : A group of atoms having a charge is known as polyatomic ion.
Examples : (NH4)+ (SO4)2–
Question. Explain the law of multiple proportions.
Ans : According to law of multiple proportions, when two elements combine to make one or more compounds then the ratio of weights of these element remain in fixed ratio to one another. For example : Hydrogen and oxygen combine to form water (H2O) and hydrogen peroxide (H2O2) under different condition. 2 grams of hydrogen combines with 16 grams of oxygen in case of water while 2 grams of hydrogen combines with 32 grams of oxygen to form hydrogen peroxide. Now, the weights of oxygen combine with a fixed weight of hydrogen in water and hydrogen peroxide respectively are 16 and 32 which are in simple ratio of 16: 32 or 1 : 2.
Question. What is meant by a molecule? Give examples.
Ans : A molecule is the smallest particle of an element or a compound capable of independent existence under ordinary conditions. It shows all the properties of the substance, e.g., molecule of oxygen is O2, ozone is O3, phosphorus is P4, sulphur is S8, etc.
Question. Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Ans : 1 g of hydrogen reacts with oxygen = 8 g 3 g of hydrogen reacts with oxygen = 8 × 3 g= 24 g
Question. Define formula unit mass. Calculate formula unit mass of NaCl (atomic mass of Na = 23u, Cl = 35.5u).
Ans : The formula unit mass is same as molecular mass which is equal to the sum of masses of atoms present in a formula unit. Formula unit mass of NaCl = (23 + 35.5) = 58.5u.
Question. Give two examples of triatomic molecules.
Ans : Carbon dioxide (CO2) and water (H2O).
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