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SCIENCE (IX) ATOMS AND MOLECULES |
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MULTIPLE CHOICE QUESTIONS
(MCQs) |
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1 |
Identify the incorrect statement. (a) Atoms are very small. They cannot be seen by the naked eye. (b) The building blocks of all matter are atoms. (c) The size of an atom is measured in nanometers. (d) None of these |
1 |
|
2 |
Which of the following statements is not true about an atom? (a) Atoms are the basic units from which molecules and ions are
formed (b) Atoms are always neutral in nature. (c) Atoms aggregate in large numbers to form the matter that we can
see, feel or touch. (d) Atoms are not able to exist Independently |
1 |
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3 |
According to the law of definite proportions: (a) total mass of reactants Is equal to the total mass of products (b) mass can neither be created nor destroyed (c) In a chemical substance, elements are always present in definite
proportions by mass (d) Both a. and b. |
1 |
|
4 |
Law of constant proportion was proposed by: (a) Lavoisier (b) Dalton (c) Proust (d) Berzelius |
1 |
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5 |
A sample of pure water, irrespective of its source contains 11.1%
hydrogen and 88.9% oxygen. The data supports: (a) law of conservation of mass (b) law of constant proportions (c) law of multiple proportions (d) Avogadro's law |
1 |
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6 |
What is the formula of carbon tetrachloride? (a) CCl4 (b) CCl3 (c) CCl2 (d) CCl |
1 |
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7 |
All noble gas molecules are: (a) monoatomic (b) diatomic (c) Both a and b (d) triatomic |
1 |
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8 |
Latin name for iron is: (a) falium (b) fatrium (c) femur (d) ferrum |
1 |
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9 |
Which law states that the total mass of the reactants is equal to the
total mass of the products in chemical reaction? (a) Law of constant proportions (b) Law of conservation of energy (c) Law of conservation of mass (d) Law of multiple proportions |
1 |
|
10 |
Atomicity of sulphur is: (a) 8 (b) 4 (c) 2 (d) 1 |
1 |
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ASSERTION AND REASON QUESTIONS
(a) Both Assertion (A) and
Reason (R) are true and Reason (R) is the correct explanation of the
Assertion (A). (b) Both Assertion (A) and
Reason (R) are true and Reason (R) is not the correct explanation of the
Assertion (A). (c) Assertion (A) is true, and
Reason (R) is false. (d) Assertion (A) is false,
and Reason (R) True. |
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11 |
Assertion (A): In a
chemical substance, the elements are always present in definite proportions
by mass. Reason (R): Atoms of
different elements have different masses as well as chemical properties. |
1 |
|
12 |
Assertion (A): Law of
conservation of mass holds good for nuclear reactions. Reason (R): It states that
mass can neither be created nor destroyed in a chemical reaction. |
1 |
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13 |
Assertion (A): The
molecular mass and formula unit mass of a substance is the sum of atomic masses
of all the atoms in the molecular formula or formula unit of a compound. Reason (R): The only
difference between the molecular mass and formula unit mass is that, former
is for molecular compounds (covalent compounds) and latter is for ionic
compounds. However, their numerical value is the same. |
1 |
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14 |
Assertion (A): Atomic mass
of aluminium is 27. Reason (R): An atom of
aluminium is 27 times heavier than 1/12th of the mass of carbon-12 atom. |
1 |
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VERY SHORT ANSWER QUESTIONS |
|
15 |
State the law of conservation of mass. |
2 |
|
16 |
As per the law of definite proportions, carbon and oxygen combine in
a ratio of 3: 8. Compute the mass of oxygen gas that would be required to
react completely with 6 g carbon. |
2 |
|
17 |
Which postulate of Dalton's atomic theory can explain the law of
definite proportions? |
2 |
|
18 |
Name the international organisation which approves the name given to
the elements? |
2 |
|
19 |
Out of atoms and molecules, which can exist independently? |
2 |
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SHORT ANSWER TYPE QUESTIONS |
|
20 |
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of acetic
acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of
sodium acetate. Show that these observations are in agreement with the law of
conservation of mass. sodium carbonate + acetic acid --------> sodium acetate + carbon dioxide + water |
3 |
|
21 |
A 0.24 g sample of 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. |
3 |
|
22 |
Write the cations and anions present (if any) in the following
compounds: (I) CH3COONa (ii) NaCl (iii) H2 (iv) NH4NO3 |
3 |
|
23 |
Give the names of the elements present in the following compounds: (i) Quick lime (ii) Hydrogen bromide (iii) Baking powder (iv) Potassium sulphate |
3 |
|
24 |
State the number of atoms present in each of the following chemical
species: (1) CO32- (ii) PO43-
(iii) P205 (iv) CO |
3 |
|
25 |
(i) Define atomic mass unit. (ii) Define molecular mass. (iii) Give an example of: (a) Diatomic (b) Triatomic molecule of compounds. |
3 |
|
26 |
Write the drawbacks of Dalton’s Atomic Theory. |
3 |
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LONG ANSWER TYPE QUESTIONS |
|
27 |
(i) Define the following terms: (a) Atomicity (b) Valency (c)
Relative atomic mass. (ii) What is a molecule? Explain with an example. (iii) What is the difference between the molecule of an element and
the molecule of a compound? Give one example of each. |
5 |
|
28 |
The percentage of three elements-calcium, carbon and oxygen in a
sample of calcium carbonate is given as: Calcium = 40 %; Carbon 12%; Oxygen
48%. If the law of constant proportion is true, what weight of these elements
will be present in 1.5 g of another sample of calcium carbonate? (Given
atomic mass of Ca= 40 u, C 12 u, O= 16 u). |
5 |
|
29 |
Write the formulae of: (i) Magnesium hydroxide (ii) Hydrogen sulphide (iii) Potassium chloride (iv) Calcium oxide (v) Barium chloride (vi) Sodium carbonate. |
5 |
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30 |
Write the molecular formulae for the following compounds: (i) Copper (II) bromide (ii) Aluminium (III) nitrate (iii) Calcium (II) phosphate (iv) Iron (III) sulphite (v) Mercury (II) chloride (vi) Magnesium (II) acetate |
5 |
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31 |
(i) How would you differentiate between a molecule of an element and
a molecule of a compound? Write one example of each type. (ii) Write the chemical formula of ammonium sulphate. (iii) During the formation of ammonia, what mass of hydrogen gas
would be required to react completely with 42 g of nitrogen gas? |
5 |
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32 |
What are the postulates of Dalton's atomic theory? |
5 |
|
33 |
(i) What do the following symbols/formulae stands for? (a) 2O (b) O2
(c) O3 (d) H2O (ii) Give the chemical formulae of the following compounds: (a)
Potassium carbonate (b) Calcium chloride (iii) Calculate the formula unit
mass of Al2(SO4)3 (Given atomic mass of Al
-27 u, S -32 u, O-16 u) (iv) Calculate the formula unit masses of ZnO and Na₂O, given atomic
masses of Zn -65 u, Na = 23 u, K = 39 u and O = 16 u. |
5 |
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CASE BASED STUDY QUESTIONS |
|
34 |
READ THE PASSAGE CAREFULLY AND
ANSWER THE FOLLOWING QUESTIONS: A compound is formed by the combination of element X with valency +2
and element Y with valency –1. 1. Write the formula of the compound formed between X and Y. 2. If the atomic mass of X = 40 and Y = 35.5, find the molecular mass
of the compound. 3. Give one example of a compound having a similar type of
combination. 4. Explain what is meant by valency. |
4 |
|
35 |
READ THE PASSAGE CAREFULLY AND
ANSWER THE FOLLOWING QUESTIONS: Magnesium reacts with oxygen to form magnesium oxide according to the
equation: A student takes 12 g of magnesium and 8 g of oxygen. After the
reaction, some magnesium remains unreacted. 1. Which reactant is limiting in this reaction? 2. Calculate the mass of magnesium oxide formed (Mg = 24, O = 16). 3. How much magnesium remains unreacted? 4. Which law of chemical combination is followed here? |
4 |
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36 |
READ THE PASSAGE CAREFULLY AND
ANSWER THE FOLLOWING QUESTIONS: When 9 g of water is decomposed by electrolysis, it produces 8 g of
oxygen and 1 g of hydrogen. In another experiment, 90 g of water gives 80 g
of oxygen and 10 g of hydrogen. 1. Which law is verified by the given data? 2. State the law of constant proportion. 3. Calculate the ratio of hydrogen to oxygen by mass in both
experiments. 4. What conclusion can you draw from the data? |
4 |
|
37 |
READ THE PASSAGE CAREFULLY AND
ANSWER THE FOLLOWING QUESTIONS: In a closed container, 4 g of hydrogen reacts completely with 32 g of
oxygen to form water. After the reaction, the total mass of the product is
found to be 36 g. 1. Which law of chemical combination is illustrated in this
experiment? 2. State this law. 3. If 8 g of hydrogen reacts with oxygen, how many grams of water
will be produced? 4. What will be the total mass of reactants and products in this
reaction? |
4 |
DOWNLAOD THE ASSIGNMENT HERE:
FOLLOW THE INSTRUCTIONS FOR DOWNLOAD THIS ASSIGNMENT:
1. SEARCH WWW.SCIENCEARENA.IN
2. OPEN EDUCATION AND RESOURCES IN MENU BAR.
3. SINGLE CLICK DOWNLOAD AVAILABLE IN DOWNLAOD SECTION.
https://www.sciencearena.in/p/education-resources.html