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Atoms And Molecules - Important Questions Model Question Paper 1 In 9th Science

Published on: 30/07/2018

Based on the chapter Atoms and Molecules, some of the important questions are prepared in this question paper.

Download CBSE Class 9th Standard CBSE Science question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 9th Standard CBSE Science

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Std: 9th Standard CBSE - Science

chapter: - Model Question paper

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Questions:

Generic 3

1 x 3 = 3

50 g 0f 10% lead nitrate is mixed with 50g of 10% sodium chloride in a closed vessel.After reaction has taken place, it was found that 6.83 g of lead chloride was precipated.Besides, the reaction mixture contained 90g water and sodium nitrate.Calculate the amount of sodium nitrate formed.

Generic 2

2 x 2 = 4

(i) Convert into mole 20 g of water (Atomic mass of hydrogen and oxygen are 1 and 16 respectively).
(ii) Convert into mole 22 g of carbon dioxide.

Write the names of the compounds represented by the following formulae.
(i) NaBr (ii) Al₂O₃ (iii) ZnNO₃ (iv) HCl (v) NaCl (vi) CaCO₃

Fill up / 1 Marks

8 x 1 = 8

Law of ............. says that hydrogen and oxygen combine in the ratio 1 : 8 to form water.

Isotopes differ from each other in ............

One mole of sodium sulphate contains ............... atoms of sodium

The abbreviations used for the lengthy names of elements are termed ............

Avogadro's number represents ................... particles of a substance.

Naturally occurring oxygen is a mixture of atoms of slightly different masses called ............

10.

Dalton's atomic theory provides explanation for the various laws of ...................

11.

The unit of atomic mass is .............

Multiple Choice Question

2 x 1 = 2

12.

In SO₂, the mass of sulphur in combination with 3.0 oxygen is

(a)

3.0 g

(b)

4.0 g

(c)

32.0 g

(d)

16.0 g

13.

Which one of the following dose not represnt molar mass of a substance?

(a)

1 mole of HCl

(b)

6.023 x 10²³ molecules of helium

(c)

16 g of O₂

(d)

44 g of CO₂

Generic 5

1 x 5 = 5

14.

(i) One mole of carbon atom weighs 12 g.Find the mass in grams of one atom of carbon (Given C = 12u, No = 6.022 x 10²³ per mole)
(ii) Calculate the mass of the following:
(a) 0.5 mole of N2 gas
(b) 0.2 mole of O-atoms
(c) 4 moles of aluminium atom
[Given, N = 14 u, 0 = 16 u, Al = 27 u,
Avogadro's number = 6.022 x 10²³ per mole ]

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Answers Key:

Generic 3

1 x 3 = 3

50 g of 10% lead nitrate means the solution contains 5 g lead nitrate and 45 g water.Similarly, 50 g of 10% sodium chloride means the solution contains 5 g sodium chloride and 45 g water.
Thus total contents before reaction = 5+5+90 = 100 g
After reaction, amount of water = 90 g
Amount of precipitate= 6.83 g
Since according to law of conservation of mass, the total mass of reaction mixture = 100 g
Amount of sodium nitrate = 100-90-6.83 = 3.17g

Generic 2

2 x 2 = 4

(i) Molecular mass of water (H₂O)
= 1 x 2 + 16 = 18u
:. Number of moles in 20 g of water =\(\frac { 20 }{ 18 } \)
(ii) 44 gm of carbon dioxide = 1 mole
22 gm of carbon dioxide = 0.5 mole

NaBr	Sodium bromide
Al₂O₃	Aluminium oxide
ZnNO₃	Zinc nitrate
HCl	Hydrogen chloride
NaCl	Sodium chloride
CaCO₃	Calcium carbonate

Fill up / 1 Marks

8 x 1 = 8

()
definite proportions

()
molar mass

()
12.046 x 10²³

()
symbols

()
6.022 x 10²³

()
isotopes

10.

()
combinations

11.

()
u

Multiple Choice Question

2 x 1 = 2

12.

(a)
3.0 g

13.

Generic 5

1 x 5 = 5

14.

(i) 1 Mole of Carbon atom = 6.022 x 10²³ atoms
6.022 x 10²³ atoms of carbon weigh = 12 g
1 atom of carbon weighs = \(\frac { 12 }{ 6.022\times { 10 }^{ 23 } } \\ \)
= 1.99 x 10^-23
(ii) (a) n = 0.5 mol; M = 14 x 2 = 28 g; m = ?
m = n x M = 0.5 x 28 = 14.0 g
(b) n = 0.2 mol; M = 16 g; m = ?
m = n x M = 0.2 x 16 = 3.2 g
(c) n = 4 mol; M = 27 g; m = ?
m = n x M = 4 x 27 = 108 g