21.  What is the correct scientific notation for 0.00016 ?

A.

B.

C.

D. cannot be determined.

Answer : Option A

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22.  How many significant digits are there in 0.25 ?

A. 1

B. 2

C. 3

D. cannot be determined.

Answer : Option B

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23.  Which of the following number contains three significant digits ?

A. 0.200

B. 0.030

C. 0.0052

D. 0.002

Answer : Option A

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24.  What is the number of neutrons in ion (Atomic mass namber = 70) (IITJEE 1979)

A. 34

B. 36

C. 38

D. 40

Answer : Option D

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25.  The same amount of Zinc is treated separately with excess of sulphuric acid and excess of sodium hydroxide. What will be the ratio of volumes of hydrogen evolved ? (IIT JEE 1979)

A. 1 : 1

B. 1 : 2

C. 2 : 1

D. 9 : 4

Answer : Option A

Explanation :

(i)

(ii)

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26.  2.76 g of silver carbonate on being strongly heated yields a residue weighing (IIT JEE 1979)

A. 2.16 g

B. 2.48 g

C. 2.32 g

D. 2.64 g

Answer : Option C

Explanation :

  1 mol         1mol

0.01 mol        0.01 mol

There fore mass of residue = 0.01 molar mass of

                                                        = 0.01 x 232

                                                        = 2.32 kg

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27.  Find the total number of electrons in one molecule of carbon dioxide.

A. 22

B. 44

C. 66

D. 88

Answer : Option A

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28.  A gaseous mixture contains oxygen and nitrogen in the ratio of 1 : 4 by weight. Therefore, the ratio of their number of molecules is

A. 1 : 4

B. 1 : 8

C. 7 : 32

D. 3 : 16

Answer : Option C

Explanation :

The ratio by weight

 Ratio of moles

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29.  Identify the incorrect unit conversion factor.

A.

B.

C.

D. None of these

Answer : Option D

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30.   on heating gives and 1.92g oxygen. Which of the following laws is illustrated by this statement ?

A. Law of definite proportion

B. Law of mass conservation

C. Law of multiple proportion

D. Avogadro’s law.

Answer : Option B

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