Fundamentals of Chemistry

9th chemistry chapter 1 solved exercise short questions

Q#1 : Define Industrial Chemistry and Analytical Chemistry .

Industrial Chemistry :

” The branch of chemistry that deals with the manufacturing of chemical compounds on commercial scale , is called Industrial Chemistry .”

• It deals with the manufacturing of basic chemicals such as oxygen , chlorine , ammonia , caustic soda , nitric acid and sulphuric acid etc .

Analytical Chemistry :

” The branch of chemistry that deals with separation and analysis of a sample to identify its components. “

• Two types of analysis are carried out .

1. Qualitative Analysis provides the identity / composition of a substance .
2. Quantitative Analysis determines the amount of each component present in the sample.

Q#2 : How can you differentiate between organic and inorganic chemistry ?

Q#3 : Give the scope of biochemistry .

Scope of Biochemistry :

• Biochemistry covers all chemical processes taking place in living organisms , such as synthesis and metabolism of biomolecules like carbohydrates , protein and fats .
• Applications of biochemistry are in the fields of medicine , food science and agriculture .

Q#4 : How does homogeneous mixture differ from heterogeneous mixture .

Q#5 : What is the relative atomic mass ? How it is related to gram ?

Relative Atomic Mass :

” The relative atomic mass of an element is the average mass of atoms of that element as compared to 1/12 th (one-twelfth) the mass of an atom of carbon-12 isotope “

• Unit = amu

Relation of amu with grams :

Unit of relative atomic mass is atomic mass unit , which is expressed in grams such as ,

Q#6 : Define Empirical Formula with an example .

Empirical Formula :

“It is the simplest whole number ratio of atoms present in molecule or formula unit of a compound . “

Example :

Glucose has simplest ratio 1:2:1 of carbon , hydrogen and oxygen respectively . Hence , its empirical formula is CH2O.

Q#7 : State three reasons why air is a mixture and water a compound ?

Air ( Mixture ):

1. Air is formed by the simple mixing up of the substances . i.e., gases , dust , water vapors etc.
2. Air does not have sharp and fix melting point .
3. In air , compounds retain their properties as a mixture as well .

Water (Compound) :

1. It is formed by the chemical combination of atoms of hydrogen and oxygen .
2. Water has a sharp and fixed melting point .
3. Water has different properties from its components .

That’s why , Air is a mixture and water is a compound .

Q#8 : Explain why hydrogen and oxygen are considered as elements whereas water as a compound .

Hydrogen and Oxygen are elements .

Reason :

Because they have same type of atoms , having same atomic number and it cannot be decomposed into simple substance by chemical means .

While Water is considered as compound .

Reason :

Because it is chemical combination of oxygen and hydrogen which lose their properties to produce water .

Q#9 : What is the significance of symbol of an element ?

Significance of the symbol :

• Symbols are used instead of writing full names , so it takes less time .
• Symbols have made easier to write formulas of the compounds.

Q#10 : State the reason soft drink is a mixture and water is a compound .

Soft Drink ( Mixture ):

• Soft drink is made up by simple mixing up of substance ( sugar , CO2 , water ) .
• The components of soft drink retain their properties in a mixture .

Water ( Compound ) :

• Water is formed by combination of atoms of hydrogen and oxygen .
• The components of water lose their properties to form compound water .

That’s why soft drink is a mixture and water is a compound .

Q#11 : Classify the following into elements , compounds and mixture .

1. He and H2 :

• Helium is an element .
• H2 is a compound .

2 . CO and Co :

• Carbon monoxide ( CO) is a compound .
• Co ( Cobalt ) is an element .

3 . Water and milk :

• Water is a compound .
• Milk is a mixture .

4 . Gold and brass :

• Gold is an element .
• Brass is a mixture ( alloy ).

5 . Iron and steel :

• Iron is an element .
• Steel is a mixture .

Q#12 : Define atomic mass unit . Why is it needed ?

Atomic Mass Unit :

” One atomic mass unit is the 1/12th the mass of an atom of carbon-12.

Need of Atomic Mass Unit :

It is needed because the mass of an atom is too small to be determined practically , so , to measure such a small mass , small scale was required which is atomic mass unit .

Q#13 : State the nature and name of the substance formed by combining the following :

Q#14 : Differentiate between molecular mass and formula mass , which of the following will be molecular formula ?

• H2O : Molecular Formula
• NaCl : Formula Units
• KI : Formula Units
• H2SO4 : Molecular Formula

Q#15 :Which one has more atoms : 10g of Al or 10g of Fe ?

10 g of Al have more atoms .

Reason :

As we know :

” If same masses are given , then the element with less atomic mass , has more number of atoms as well . “

That’s why , 10 g of Aluminum will have more atoms .

Q#16 : Which one has more molecules . 9g of water or 9g of sugar (C12H22O11 ) ?

9g of water has more molecules .

Reason:

we know that :

” If same masses are given , then the compounds with less molecular mass will have more number of moles and more number of molecules as well.”

Hence , water has less molecular mass , so it has more number of molecules in 9grams than sugar .

Q#17 : Which one has more formula units : 1g of NaCl or 1g of KCl ?

1g of NaCl has more formula units :

Reason :

we know that :

” If same masses are given , then the with less formula mass will have more number of moles and more number of formula units as well .”

That’s why . 1g NaCl has more formula units due to low formuls mass than KCl .

Q#18 : Differentiate between homoatomic and heteroatomic molecules with example .

Q#19 : In which one of the following case the number of hydrogen atoms is more ?

2 moles of HCl or 1 mole of NH3

( Hint : 1 mole of a substance contain the same number of moles of atoms as are in 1 molecule of a substance )

• NH3 has more hydrogen atoms than HCl .

Reason / Calculation :

Hydrogen atom in HCl = 1

Hydrogen atom in 1 mole of HCl = 1 mole of H atoms

Hydrogen atoms in 2 mole of HCl = 2 moles of H atoms

But ,

Hydrogen atoms in 1 mole of NH3 = 3 moles of H atom

Hence , NH3 has more Hydrogen atoms than HCl .