ATOMS AND MOLECULES 9

Practice Paper

Subject Chemistry (2020)

 CH- 3  Atoms and Molecules 

Class IX

I. Short answer type questions:                 

1. Who provides the basic theory about the nature of matter?
2. State Dalton's atomic theory.
3. What are binary compounds?
4. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
5. Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
6. What is an Atom?
7. What is Avogadro's number or constant?
8. Write the full forms of IUPAC.
9. What is the difference between CO and Co?
10. Write the symbol and Latin names of elements  - Iron, sodium, and potassium.
11. Why is it not possible to see an atom with naked eyes?
12. What is a Molecule?
13. Define valency.
14. How atom do exists?
15. What is the difference between 2H and H_2.?
16. What is an ion?
17. Name the anion and cation which constitute the molecule of Sodium chloride?
18. How many atoms are there in 1 gm of hydrogen?
19. Define the ionic compound?
20. Define molecular mass?
21. What is the difference between the formula unit mass and molecular mass?
22. Define mole. 
23. Write the name of elements present in the common salt sample?
24. Define Avogadro's number.
25. The chemical formula of a metal Sulphate is MSO₄. What will be the formula of its chloride?
26. Write the chemical formula of ammonium chloride and sodium phosphate?
27. Define the atomic mass.

II. Short answer type questions:

1. What are the Laws of Chemical Combination?
2. How do atoms exist?
3. What is Dalton's atomic theory?
4. 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?
5. Define chemical formula. How many atoms are present in a
   (i) H₂S molecule and (ii) PO₄^-2 ion?
6. Define polyatomic ion. Name two elements that exist as independent atoms?
7. Define the atomic mass unit and relative atomic mass.
8. (a)Define atomicity.
   (b)Write the atomicity of the following molecules:
   (i) H₂SO₄  (ii) CCl₄
9.  Valency of an element X is 3 while that of Y is 1.Write the formula of the compounds formed when each of them separately combines with oxygen?
10. What is the formula unit mass? Calculate the formula unit masses of ZnO, Na₂O, K₂CO₃, (NH₄)₂CO₃ (given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u).
11. Calculate the molecular masses of
    H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH.
12. If 12 gm of carbon is burnt in the presence of 32 gm oxygen, how much carbon dioxide will be formed?
13. Calculate the molar mass of (i) Sulphur molecule (ii) Ethyne (iii)Phosphorus molecule.
14. Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, the atomic mass of Na = 23 u, Fe = 56 u)?
15. Calculate the number of molecules of sulphur (S₈) present in 16 g of solid sulphur.
16. Calculate the formula unit mass of CaCl₂.
    (a) Calculate the relative molecular mass of water (H₂O).
    (b) Calculate the molecular mass of HNO₃

III. Long answer type questions:

1. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.
   sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water.
2. Write the symbols of (i) Silver (ii) Mercury (iii) Magnesium (iv) Chromium?
3. (a) Write a chemical formula of a compound using zinc ion, phosphate ion, Sodium carbonate, lead carbonate, and Ammonium chloride?
   (b) Calculate the ratio by mass of atoms present in a molecule of carbon dioxide (CO₂).
4. Write down the names of compounds represented by the following formulae:
   (i) Al₂(SO₄)₃ (ii) CaCl₂ (iii) K₂SO₄ (iv) KNO₃ (v) CaCO₃.
5. Define
   (ii) Diatomic
   (iii) Triatomic
   (iv)Tetra atomic
   (v) A polyatomic molecule of elements.
6. What is the modern-day symbol of atoms of different elements Hydrogen, Carbon, Oxygen, Phosphorous, Sulphur, Iron, Copper, Lead, Silver, Gold, Platinum, and Mercury?
7. Calculate the no. of moles in (i) 17 gm of H₂O (ii) 5.75 gm of sodium (iii)52 gm of He  (iv) 34 gm of NH₃. 60 gm. of  Ca.
8. (a) Calculate the no. of molecules in 8 gm of oxygen?
   (b) 5 gm of calcium combines with 2gm of oxygen to form a compound. Find the molecular formula of the compound. (A.M of Ca=40u O=16u).
9. Write the chemical formula of bicarbonates of Na⁺, K⁺¹, Al⁺³, Mg⁺², Ca^+2, and Zn⁺².
10. The percentage of three elements Ca, C and O₂ in a sample of calcium carbonate is given as Ca=40%, C=12.0%, O=48%. If the law of proportion is true, what weights of these elements will be present in 1.5g of another sample of Ca Carbonate? (A.m. of Ca=20, C=12 O=16).
11.  (a) An element X has valency 3. Write the chemical formula of its chloride. 
    (b) If an element Y has valency 2 then write the chemical formula of its potassium salt?
12. Calculate the number of moles for the following:
    (i) 52 g of He (finding mole from mass) 
    (ii) 12.044 ×10²³  number of He atoms (finding mole from a number of particles).
    (iii) 3.011 x 10²³ no. of oxygen atoms.
13. Calculate the number of moles for the following:
    (i) 0.5 mole of N₂ gas
    (ii) 0.5 mole of N atoms
    (iii) 3.011 × 10²³ number of N atoms.
    (iv) 6.022 × 10²³ number of N₂ molecules.
14. When 3.0 g of carbon is burnt in 8.00 g of oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
15. A 0.24 gm of a sample of a compound of oxygen and boron was found by analysis to contain 0.096 gm of boron and 0.144 gm of oxygen.
    (i) Calculate the % composition of the compound by weight.
    (ii) Find the no. of moles in 0.144g of oxygen gas. 
16. Write the chemical formulae of the following.
    (a) Magnesium chloride
    (b) Calcium oxide
    (c) Copper nitrate
    (d) Aluminium chloride
    (e) Calcium carbonate.
17. Give the names of the elements present in the following compounds.
    (a) Quick lime
    (b) Hydrogen bromide
    (c) Baking powder
    (d) Potassium Sulphate.
18. Calculate the molar mass of the following substances.
    (a) Ethyne - C₂H₂
    (b) Sulphur molecule - S₈
    (c) Phosphorus molecule - P₄ (Atomic mass of phosphorus = 31)
    (d) Hydrochloric acid - HCl
    (e) Nitric acid - HNO₃
19. What is the mass of—
    (a) 1 mole of nitrogen atoms?
    (b) 4 moles of Aluminium atoms (Atomic mass of Aluminium = 27)?
    
    (c) 10 moles of sodium sulphite (Na₂SO₃)? 
20. _{Calculate the number of Aluminium ions present in 0.051 g of Aluminium
    oxide.
    (Hint: The mass of an ion is the same as that of an atom of the same element. The atomic mass of Al = 27 u)}
21. _{Write down the formulae of
    (i) Sodium oxide
    (ii) Aluminium chloride
    (iii) Sodium sulphide
    (iv) Magnesium hydroxide.}
22. _{Convert into a mole.
    (a) 12 g of oxygen gas
    (b) 20 g of water
    (c) 22 g of carbon dioxide.}
23. _{Calculate the no of particles in each of the following:
    (i) 7g of nitrogen molecules
    (ii) 0.5 mole of carbon atoms.
    (iii) 8 gm of oxygen molecule.
    (iv) 0.1 mole of carbon.
    (v) 46 g of Na atoms.(Given  N=14, C=12, N0=6.022x}10²³)

NCERT QUESTIONS:

1. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass. sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water 
2. 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? 
3. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass? 
4. Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
5. Define the atomic mass unit. 
6. Why is it not possible to see an atom with naked eyes?
7. Write down the formulae of (i) sodium oxide (ii) aluminium chloride (iii) sodium suphide (iv) magnesium hydroxide.
8. Write down the names of Q compounds represented by the following formulae: (i) Al₂(SO₄)₃ (ii) CaCl₂ (iii) K₂SO₄ (iv) KNO₃ (v) CaCO₃. 
9. What is meant by the term chemical formula? 
10. How many atoms are present in a (i) H2S molecule and (ii) PO4 3– ion?
11. Calculate the molecular masses of H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH. 
12. Calculate the formula unit masses of ZnO, Na₂O, K₂CO₃, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
13. If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
14. 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. Calculate the percentage composition of the compound by weight.
15. When 3.0 g of carbon is burnt in 8.00 g of oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer? 
16. What are polyatomic ions? Give examples.
17. Write the chemical formulae of the following. 
    (a) Magnesium chloride 
    (b) Calcium oxide 
    (c) Copper nitrate 
    (d) Aluminium chloride 
    (e) Calcium carbonate.
18. Give the names of the elements present in the following compounds. 
    (a) Quick lime 
    (b) Hydrogen bromide 
    (c) Baking powder 
    (d) Potassium sulphate.
19. Calculate the molar mass of the following substances. 
    (a) Ethyne, C₂H₂ 
    (b) Sulphur molecule,S₈
    (c) Phosphorus molecule, P₄ (Atomic mass of phosphorus = 31) 
    (d) Hydrochloric acid, HCl 
    (e) Nitric acid, HNO₃ .
20. What is the mass of—
    (a) 1 mole of nitrogen atoms? 
    (b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
    (c) 10 moles of sodium sulphite (Na₂SO₃)? 
21. Convert into a mole.
    (a) 12 g of oxygen gas 
    (b) 20 g of water 
    (c) 22 g of carbon dioxide.
22. What is the mass of: 
    (a) 0.2 mole of oxygen atoms? 
    (b) 0.5 mole of water molecules?
23. Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.
24.  Calculate the number of aluminium ions present in 0.051 g of aluminium oxide. (Hint: The mass of an ion is the same as that of an atom of the same element. The atomic mass of Al = 27 u).

CHAPTER 1 - MATTER IN OUR SURROUNDINGS	☛ QUESTION WITH SOLUTIONS
CHAPTER 2 - IS MATTER AROUND US PURE?	☛QUESTION WITH SOLUTIONS
CHAPTER 3 - ATOMS AND MOLECULES	☛ QUESTION WITH SOLUTIONS
CHAPTER 4 - STRUCTURE OF ATOM	☛   QUESTION WITH SOLUTIONS
CHAPTER 5 -  THE FUNDAMENTAL UNIT OF LIFE
CHAPTER 6 -  TISSUE
CHAPTER 7 -   DIVERSITY IN LIVING ORGANISM
CHAPTER 8 -  MOTION	☛ QUESTION WITH SOLUTIONS
CHAPTER 9 -  FORCE AND LAW OF MOTION	☛  QUESTION WITH SOLUTIONS
CHAPTER 10 - GRAVITATION	☛ QUESTION WITH SOLUTIONS
CHAPTER 11 -  WORK AND ENERGY
CHAPTER 12 -  SOUND
CHAPTER 13-  WHY DO WE FALL ILL
CHAPTER 14 - NATURAL RESOURCES
CHAPTER 15 - IMPROVEMENT OF FOOD RESOURCES