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An important facility for 9th class students preparing for short questions chemistry 9th class chapter 4 of BISE. Get hundreds of questions to prepare and get better marks in 9th chemistry
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Question: 1
Ionic compounds are solids. Justify.
Answer: 1
Ionic compounds are made up of positively and negatively charged ions. Thus, they consist of ions and not the molecules. These positively and negatively chareed ions are held together in a solid or crystal form with strong electrostatic attractive forces. So, ionic compounds are solid in nature.
Question: 2
Why a covalent bond becomes polar?
Answer: 2
When there is a difference of electronegativity between two covalently bonded atoms there will be unequal attraction for the bond pair of electrons between such atoms. It will result in the formation of polar covalent bond.
Question: 3
What is ionic bond? Give an example.
Answer: 3
A chemical bond which is formed due to complete transfer of electron from one atom to another atom is called ionic bond.
Question: 4
What is meant by VanderWaalsforces?
Answer: 4
All intermolecular forces, which are collectively called Vander Waals forces, are in electricalin nature.
Question: 5
What is triple covalent bond, explain with an example?
Answer: 5
When each bonded atom contributes three electrons, three bond pairs are involved in bond formation . This type is called triple covalent bond. Three small lines are used to indicate these three pairs of electrons between those atoms in the molecules of such compounds. For example N2 & C2H2
Question: 6
Metals are good conductor of electricity. Why?
Answer: 6
Metals are good conductors of electricity because metals have free electrons which are mobile in nature. Spaces are present among the atoms. Mobile electrons can move freely in these spaces. Hence, movement/flow of electrons is known as electricity that's why metals are good conductor of electricity.
Question: 7
Define chemical bond.
Answer: 7
A chemical bond is defined as a force of attraction between atoms that holds them together in a molecule.
Question: 8
Why does ice float on water?
Answer: 8
Floating of ice on water is because of hydrogen bonding . The density of lice at 0 Degree centigrade . In the liquid state water molecules move randomly. However, water freezes, the molecules arrange themselves in an ordered form, that gives them open structure. This process expands the molecules that results in ice being less dense as compared to water
Question: 9
Why do atoms form chemical bonds?
Answer: 9
Atoms achieve stability by attaining electronic configuration of inert gases ns2 or ns2. Atoms combine with one another, which is called chemical bond.
Question: 10
What is relationship between electronegativity and polarity?
Answer: 10
Electronegativity values of the atoms play a very important role in polarity of compounds. These two terms have direct relationship with one another, because of electronegativity difference is high then more polar bond will be and vice versa.
Question: 11
Why noble gases are non-reactive?
Answer: 11
The noble gases do have 2 or 8 electrons in their valence shells. It means all the noble gases have their valence shells completely filled . Their atoms do not have vacant space in their valence shell to accommodate extra electrons. therefore noble gases do not gain, lose or share electrons. That's why they aare non-reactive.
Question: 12
What type of covalent bond is formed in nitrogen molecule?
Answer: 12
In nitrogen molecule, three bond pairs are involved in bond formation. This type is called triple covalent bond. Three small lines are used to indicate these three pairs of electrons between those atoms in the molecules of such compounds.
Question: 13
What type of elemetns have tendency of sharing of electrons?
Answer: 13
If bond formation is between similar atoms or between the atoms that have comparable electronegativities, then the chemical bond formation is by sharing of electrons.
Question: 14
Give properties of Ionic compound?
Answer: 14
1- They Conduct electricity, but only when they are dissolved in water.
2- They are hard
Question: 15
Why does sodium form a chemical bond with chlorine?
Answer: 15
Sodium losses one electron and chlorine accept one electron to complete its octet. Because sodium is electropositive and lose electron and becomes stable while chlorine is electronegative it gains one electron from sodium and complete its octet and becomes stable . Hence sodium forms chemical bond with chlorine.
Question: 16
Why big size covalent molecules have high melting and boiling points.
Answer: 16
Bigger molecules with three dimensional bonding form covalent crystals which are very stable and have high melting and boiling points.
Question: 17
What id difference between polar and non-polar covalent bond?
Answer: 17
Bonds that are partly ionic are called polar covalent bond
Question: 18
Difference between Duplet rule and Octet rule?
Answer: 18
Duplet rule:
Attaining two electrons in the valance shell is called duplet rule.
Question: 19
Why ionic compounds easily dissolve in water?
Answer: 19
They dissolve easily in water because water is a polar solvent and has high dielectric constant that weakens the attraction between ions.
Question: 20
Write molecule is polar how?
Answer: 20
A Polar molecule forms when an atom of high electronegativity such as chlorine, bonds with a less electronegative atom such as hydrogen.
Question: 21
Define double covalent bond?
Answer: 21
When each bonded atom contributes two electrons, two bond pairs are shared and a double covalent bond is formed.
Question: 22
Why is BF3 electron deficient?
Answer: 22
In BF3 molecule, three valence electrons of boron atom pair up with three electrons. One from each of three fluorine atoms. The boron atom even after the sharing of electron remain shortage of 2 electrons in its outer most shell.
Question: 23
Why a chemicalbond is formed
Answer: 23
Chemical bonds may be formed by complete transfer of electrons; mutual sharing or by donation from an atom.
Question: 24
Why are dipole forces of attraction not found in halogen molecules?
Answer: 24
Dipole forces of attraction do not found in halogen molecules because they have same electronegativity and there is equal sharing of electrons.
Question: 25
What is meant by bonding electron?
Answer: 25
The valence electrons, which are involved in chemical bonding, are termed as bonding electrons.
Question: 26
Why does oxygen molecule not form a polar covalent bond.
Answer: 26
In oxygen molecule there are two same atoms and have same electronegativity. Hence oxygen molecule does not form a polar covalent bond.
Question: 27
Define dipole-dipole inteaction?
Answer: 27
The net forces of attraction between oppositely charged ends of two adjacent molecules . These attractive forces are called dipole-dipole interaction.
Question: 28
What is meant by Covalent bond?
Answer: 28
This type of bond, which is formed due to mutual sharing of electron.
Question: 29
Why the electrons move freely in metals?
Answer: 29
This is because the valence shell electrons loosely held by nucleus of an atom.there is the weak force of attraction present between nucleus and the mobile valence electrons. Therefore valence electrons move freely in metals.
Question: 30
Why ice floats on the surface of water?
Answer: 30
Floating of ice on water is because of hydrogen bonding.The density of ice at 0°C is less than that of liquid water at 0°C
Question: 31
What is meant by bond pair?
Answer: 31
The electrons that pair up to form a chemical bond are called bond pair.
Question: 32
What types of electron pairs make a molecule good donor?
Answer: 32
The Ionic pair of electron make a molecule good donor
Question: 33
Write two difference between ionic and covalent compounds?
Answer: 33
Ionic bond.
It has high polarity
its melting point was high
Question: 34
Define Ionic bond?
Answer: 34
This type of chemical bond , which is formed due to complete transfer of electron from one atom to another atom is called ionic bond.
Question: 35
What types of attractive forces exist between HCL molecules?
Answer: 35
Dipole-dipole attractive forces exist in between HCL molecules.
Question: 36
Define intermolecular forces.
Answer: 36
Along the strong forces, relatively weak forces also exist in between molecules called intermolecular force.
Question: 37
Define Co ordinate covalent bond?
Answer: 37
Their property are mostly similar to those of covalent compounds. As the nuclei in these compounds are held by shared pair of electrons, Therefore, they do not form ions in water.
Question: 38
What is meant by Intermolecular forces?
Answer: 38
The forces that hold atoms in a compound are chemical bonds, In addition to these strong bonding forces, relatively weak forces also exist in between the molecule.
Question: 39
What is meant by triple covalent bond?
Answer: 39
When each bonded atom contributes three electrons, three bond pairs are involved in bond formation. Thid type is called triple covalent bond.
Question: 40
What do you mean by dipole induced forces?
Answer: 40
When partial positive and partial negative charges exist at different positions in a molecule, the adjacment molecules with arrange themselves in such a way that negative portion of that molecules come near to positive portion of other molecule it results in a net forces of attraction between oppositely charged potions of two adjacent molecules.