Tag: chemistry

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Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids
In a cubic structure of diamond which is made from X and Y, where X atoms are at the corners of the cube and Y at the face centres of the cube. The molecular formula of the compound is
  1. $X _2Y$
  2. $X _3Y$
  3. $XY _2$
  4. $XY _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a cubic unit cell, corner atoms (X) contribute 8 * (1/8) = 1 atom. Face-centered atoms (Y) contribute 6 * (1/2) = 3 atoms. The ratio of X to Y is 1:3, resulting in the formula XY3.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

What is a metallic bonding?

  1. The chemical bonding that takes place from the attraction of metal atoms and the surrounding sea of electrons.

  2. The chemical bonding that takes place from the attraction of metal atoms and the other elements.

  3. The chemical bonding that takes place between metal atoms when they share electrons.

  4. The chemical bonding between electrons.

  5. The chemical bonding that takes place between metal atoms when they transfer electrons.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Metallic bonding: The chemical bonding that takes place from the attraction of metal atoms and the surrounding sea of electrons.
Metallic bonding is the force of attraction between valence electrons and metal ions. It is the sharing of many detached electrons between many positive ions, where the electrons act as a "glue" giving the substance a definite structure. It is unlike covalent or ionic bonding

The electrons and the positive ions in the metal have a strong attractive force between them. Therefore, metals often have high melting or boiling points. The principle is similar to that of ionic bonds.


Hence, the correct option is $\text{E}$

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Silicon carbide is a giant molecule having:

  1. covalent bond

  2. ionic bond

  3. molecular bond

  4. van der waal bond
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Electronegativity of silicon $= 1.9$
Electronegativity of carbon $= 2.55$
Electronegativity difference $= 2.55 - 1.9 = 0.65$ (Low) (less than $1.6$)
Hence the bond between $Si$ and $C$ in silicon carbon $(SiC)$ in covalent.
Multiple choice chemistry particle nature, basic units history of atomic model atomic theory of dalton daltons atomic theory

According to Dalton's atomic theory, the smallest particle in which matter can exist is called :

  1. an atom.

  2. an ion.

  3. an electron.

  4. a molecule.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DALTON'S ATOMIC THEORY :

1. Matter is made up of very small undivisible particle called atoms.

2. All the atoms of a given element is identical in all respect i.e. mass, shape, size, etc.

3. Atoms cannot be created nor destroyed by any chemical process.

4. Atoms of different elements are different in nature.

Multiple choice chemistry particle nature, basic units history of atomic model atomic theory of dalton daltons atomic theory

The atom is indivisible was proposed by :

  1. Rutherford

  2. Dalton

  3. Bohr

  4. Einstein
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

John Dalton considered that " all matter is composed of small particle called the atom."
According to Dalton: 
-Atom is the smallest indivisible part of matter which takes part in the chemical reaction.
-Atom is neither created nor be destroyed.

Multiple choice chemistry particle nature, basic units history of atomic model atomic theory of dalton daltons atomic theory

The valence electrons of an element are responsible for :

  1. physical properties of an element

  2. chemical properties of an element

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Valence electrons are electrons in the outermost shell and they are responsible for determining the number of bond formation and an atoms charge.This give the atom its chemical properties.

Multiple choice chemistry particle nature, basic units history of atomic model atomic theory of dalton daltons atomic theory

Dalton viewed chemical change as :

  1. a transfer of electrons

  2. a transfer of protons

  3. a rearrangement of atoms

  4. a change of atoms from one type into another
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dalton Atomic theory postulates-

1.  All matter is made up of atoms
2. All atoms of a given element are identical in mass and properties
3. Compounds are formed by combining two or more different kind of atoms.
4. A chemical reaction is a rearrangement of atoms.