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 .
- Qualitative Analysis provides the identity / composition of a substance .
- 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 . “
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 ):
- Air is formed by the simple mixing up of the substances . i.e., gases , dust , water vapors etc.
- Air does not have sharp and fix melting point .
- In air , compounds retain their properties as a mixture as well .
Water (Compound) :
- It is formed by the chemical combination of atoms of hydrogen and oxygen .
- Water has a sharp and fixed melting point .
- 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 .
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 .
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 .
- 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 .
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 .
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 :
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
Hydrogen atoms in 1 mole of NH3 = 3 moles of H atom
Hence , NH3 has more Hydrogen atoms than HCl .