Match column I with column II and mark the correct option from the given codes. Column I Column II (a) 28 g of He (i) 58 . 5 u (b) 0 . 5 mole of O 2 (ii) 7 mol (c) Molecular mass of common salt (iii) 60 g (d) 1 . 5 mole of Ca (iv) 16 g

(a) - (ii), (b) - (iv), (c) - (i), (d) - (iii)

(a) - (iv), (b) - (ii), (c) - (iii), (d) - (i)

(a) - (ii), (b) - (i), (c) - (iii), (d) - (iv)

(a) - (ii), (b) - (iv), (c) - (iii), (d) - (i)

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9th Foundation

IMPORTANT

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An element $X$ forms an oxide with formula $X_{2} O_{3}$ . The formula of its sulphate and phosphate will be respectively.

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Important Questions on Atoms and Molecules

MEDIUM

9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 7

Which of the following statements are incorrect?
I Phosphate ion is a trivalent and positive ion.
II Calcium ion is trivalent and positive.
III Phosphorus is a polyatomic molecule.
IV Aluminium ion is divalent and positive.

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 8

Fill in the blanks by selecting the option with the correct sequence of words. The symbolic representation of a molecule showing actual number of various atoms present in it is called its X formula. The number of atoms of all elements present in a molecule is known as its Y. Z formula gives the simplest ratio of atoms present in one molecule of the compound.

	X	Y	Z
(A)	Chemical	Valency	Molecular
(B)	Molecular	Valency	Chemical
(C)	Empirical	Atomicity	Molecular
(D)	Molecular	Atomicity	Empirical

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 9

A sample of ammonia weighs

4 g

. What mass of sulphur dioxide contains the same number of molecules as are in

4 g

of ammonia?

HARD

9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 10

An ionic compound of element

M

and chlorine has the formula,

{MCl}_{3}

. The molecular mass of

{MCl}_{3}

118.5

. What will be the molecular mass of the oxide of element

M

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 11

A given sample of sulphur contains

0.25

mol of sulphur molecules. The number of moles of sulphur atoms, number of sulphur molecules and number of sulphur atoms present in the given sample are respectively

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 12

206 g

of molten sodium bromide is decomposed electrolytically. The maximum mass of sodium obtained is [Atomic mass of

Na = 23 u, Br = 80 u

]

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 13

Four different experiments were conducted in the following ways :
I

3 g

of carbon was burnt in

8 g

of oxygen to give

11 g

{CO}_{2}

.
II

1.2 g

of carbon was burnt in air to give

4.2 g

{CO}_{2}

.
III

4.5 g

of carbon was burnt in enough air to give

11 g

{CO}_{2}

.
IV

4 g

of carbon was burnt in oxygen to form

30.3 g

{CO}_{2}

.
Law of constant proportions is illustrated in experiment(s)

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9th Foundation

IMPORTANT

NSO Science Olympiad Workbook Grade 9>Chapter 3 - Atoms and Molecules>EXERCISES>Q 14

Match column I with column II and mark the correct option from the given codes.

Column I		Column II
(a)	$28 g$ of $He$	(i)	$58.5 u$
(b)	$0.5$ mole of $O_{2}$	(ii)	$7 mol$
(c)	Molecular mass of common salt	(iii)	$60 g$
(d)	$1.5$ mole of $Ca$	(iv)	$16 g$

An element X forms an oxide with formula X2O3. The formula of its sulphate and phosphate will be respectively.

Important Questions on Atoms and Molecules

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An element $X$ forms an oxide with formula $X_{2} O_{3}$ . The formula of its sulphate and phosphate will be respectively.