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Q:

Which of the following is called 'the King of Chemicals' ?

A) Nitric acid B) Hydrochloric acid
C) Silver nitrate D) Sulphuric acid

Answer:   D) Sulphuric acid



Explanation:

Sulphuric acid is called the King of Chemicals because it is used in the preparation of a very large number of other useful chemicals such as hydrochloric acid, nitric acid, dyes, drugs etc. In fact the annual production of shulpuric acid in a country is a measure of the economy of the country.

Subject: Chemistry
Q:

Iron rusting, chemical or physical change

A) Chemical B) Physical
C) Both A & B D) None of the above
 
Answer & Explanation Answer: A) Chemical

Explanation:

In rusting the Iron ore make a chemical reaction with the oxygen in the presence of water and environmental or atmospheric moisture to produce an Iron oxide. Iron oxide is otherwise called as rust.


The rusting of iron is a chemical change because it is two substances reacting together to make a new substance.

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Q:

When combining with nonmetallic atoms, metallic atoms generally will

A) Lose electrons and forms cations B) Gain electrons and forms anions
C) Lose electrons and forms anions D) Gain electrons and forms cations
 
Answer & Explanation Answer: A) Lose electrons and forms cations

Explanation:

When combining with nonmetallic atoms, metallic atoms generally will Lose electrons and forms cations.

 

As the ionization energy of te metals are very low, so they can easily lose electrons and form positively charged ion called cations.

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Q:

Which statement is true of all atoms that are anions?

A) The atom has fewer protons than does a neutral atom of the same element. B) The atom has more protons than electrons.
C) The atom has more neutrons than protons. D) The atom has more electrons than protons.
 
Answer & Explanation Answer: D) The atom has more electrons than protons.

Explanation:

Anions are atoms or radicals (groups of atoms), that have gained electrons. Since they now have more electrons than protons, anions have a negative charge.

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Q:

The reactivity of an atom arises from 

A) the existence of unpaired electrons in the valence shell B) the energy differences between the electron shells
C) the sum of the potential energies of all the electron shells D) the average distance of the outermost electron shell from the nucleus
 
Answer & Explanation Answer: A) the existence of unpaired electrons in the valence shell

Explanation:

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

 

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

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Q:

Water is an example of?

A) Element B) Molecule
C) Compound D) Both B & C
 
Answer & Explanation Answer: D) Both B & C

Explanation:

Why Water Is Not an Element :

An element is a substance consisting of only one type of atom. Water consists of two types of atoms: hydrogen and oxygen.

 

water is both a molecule and a compound :

A compound forms whenever two or more atoms form chemical bonds with each other. The chemical formula for water is H2O, which means each molecule of water consists of one oxygen atom chemically bonded to two hydrogen atoms.

Thus, water is a compound.

 

It's also a molecule, which is any chemical species formed by two or more atoms chemically bonded to each other. The terms molecule and compound mean the same thing and can be used interchangeably.

 

Hence, water is both a molecule and a compound.


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Q:

Milk is an example of a

A) Emulsion B) Solution
C) Gel D) Suspension
 
Answer & Explanation Answer: A) Emulsion

Explanation:

Milk is an emulsion of oil in water (o/w).


Emulsion: A suspension of droplets of one liquid in another.

Constituents of milk :

The principal constituents of milk are water, fat, proteins, lactose (milk sugar) and minerals (salts). Milk also contains trace amounts of other substances such as pigments, enzymes, vitamins, phospholipids (substances with fatlike properties), and gases.

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Q:

Intermolecular forces in HCl are

A) Hydrogen bonding B) Dipole-dipole
C) Dispersion force D) All the above
 
Answer & Explanation Answer: D) All the above

Explanation:

Intermolecular forces :

The forces of attraction present in between the molecules or atoms or compounds is termed as intermolecular forces.


The molecule HCl is composed of hydrogen and chlorine atom. There is high difference in electronegativities therefore, it is polar in nature. The H end of HCl is permanently slightly positive charge. The Cl end of HCl has a permanent slight negative charge. the "H" in one molecule is attracted to the "Cl" in a neighbor. The intermolecular force is weak compared to a covalent bond. But this dipole-dipole interaction is one of the stronger intermolecular attractions.

It also has hydrogen bonding and dispersion forces. 

Dispersion forces are the weakest forces which are present in between all molecules or atoms.
Hydrogen bonds are present in molecules having at least one H-A bond where A is the strong electronegative atom (mainly F, Cl and N).

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Q:

What is the bond order of O2?

A) 1.5 B) 2
C) 2.5 D) 1
 
Answer & Explanation Answer: B) 2

Explanation:

The number of bonds between a pair of atoms is called the bond order.

Bond orders can be calculated from Lewis structures, which are the heart of the valence-bond model. Oxygen, for example, has a bond order of two.

Structure

When there is more than one Lewis structure for a molecule, the bond order is an average of these structures. The bond order in sulfur dioxide, for example, is 1.5  the average of an S-O single bond in one Lewis structure and an S=O double bond in the other.

Structures

In molecular orbital theory, we calculate bond orders by assuming that two electrons in a bonding molecular orbital contribute one net bond and that two electrons in an antibonding molecular orbital cancel the effect of one bond. We can calculate the bond order in the O2 molecule by noting that there are eight valence electrons in bonding molecular orbitals and four valence electrons in antibonding molecular orbitals in the electron configuration of this molecule. Thus, the bond order is two.

Equation

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