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IMPORTANT
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One nm is equal to:

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Important Questions on Atoms and Molecules

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9th CBSE
IMPORTANT
Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 69
The scientist who proposed the first letter (or first letter and another letter) of the Latin or English name of an element as its symbol, was:
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9th CBSE
IMPORTANT
Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 70
The atoms of which of the following pair of elements are most likely to exist in free state?
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9th CBSE
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Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 71
Which of the following elements has the same molecular mass as its atomic mass?
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9th CBSE
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Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 72
In water, the proportion of oxygen and hydrogen by mass is :
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9th CBSE
IMPORTANT
Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 73
In hydrogen peroxide (H2O2), the proportion of hydrogen and oxygen by mass is: 
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9th CBSE
IMPORTANT
Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Multiple Choice Questions (MCQs)>Q 74
The symbols of the elements cobalt, aluminium, helium and sodium respectively written by a student are as follows. Which symbol is the correct one? 
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9th CBSE
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Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Questions Based on High Order Thinking Skills (HOTS)>Q 75

Copper sulphate reacts with sodium hydroxide to form a blue precipitate of copper hydroxide and sodium sulphate. In an experiment, 15.95 g of copper sulphate reacted with 8.0 g of sodium hydroxide to form 9.75 g of copper hydroxide and 14.2 g of sodium sulphate. Which law of chemical combination is illustrated by this data? Give reason for your choice.

 

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Science for Ninth class Part 2 Chemistry>Chapter 3 - Atoms and Molecules>Questions Based on High Order Thinking Skills (HOTS)>Q 76

Potassium chlorate decomposes on heating, to form potassium chloride and oxygen. When 24.5 g of potassium chlorate is decomposed completely, then 14.9 g of potassium chloride is formed. Calculate the mass of oxygen formed. Which law of chemical combination have you used in solving this problem?