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Question 1

define EMF

Answer 1

Electromotive force (EMF) is equal to the terminal potential difference when no current flows.

Question 2

Define Electrochemical cell

Answer 2

An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions.

Question 3

define electrochemical series

Answer 3

an electrochemical series is a list that describes the arrangement of elements in the order of increasing electrode potential values.

Question 4

Define Photoelectric effect

Answer 4

The phenomenon of emmison of electrons when electromagnetic radiation strikes against them is called photoelectric effect.

Question 5

Define oxidant and reductant

Answer 5

The element that is oxidised is reducing agent or reductant because the element loses electrons, and the element that is reduced is an oxidizing agent or oxidant because the element gains electrons.

Question 6

define oxidation and reduction

Answer 6

Oxidation is the gain of oxygen while reduction is the loss of oxygen in a chemical reaction.

Question 7

What are the isotopes of hydrogen

Answer 7

Protium(0 neutrons, mass number 1) deuterium(1,2), tritium.(2,3)

Question 8

Difference between ortho and para hydrogen

Answer 8

Molecules of hydrogen in which the spins of both the nuclei are in the same directions are called ortho hydrogen. while molecules of hydrogen in which the spins of both the nuclei are in the opposite directions are called para hydrogen.

Question 9

Define Covalent hydrites

Answer 9

These hydrites are formed by the combination of elements of comparatively higher electronegativity as of p-block elements.

Question 10

Define Ionic hydrides

Answer 10

Ionic hydrides are the combination of hydrogen with metals which are highly electropositive in nature.

Question 11

Define metallic hydrides

Answer 11

Metallic hydrides are hard, conduct electricity, have a metallic lustre and have significant magnetic properties.

Question 12

why is water amphoteric

Answer 12

water can act as a base towards acids stronger than itself and as an acid towards bases stronger than itself.

Question 13

what is heavy water

Answer 13

chemically heavy water is deuterium oxide (D2O). Ordinary water contains a small portion of deuterium. It can be prepared by prolonged electrolysis of water or fractional distillation.

Question 14

uses of heave water

Answer 14

as a moderator
Heavy water has been finding use in nuclear reactors as a moderator because it slows down the fast moving neutrons and helps in controlling the nuclear fission process.

for preparation of deuterium
heavy hydrogen or deuterium can be obtained by electrolysis of heavy water or by its decomposition by sodium metal.

Question 15

Cause of hardness of water

Answer 15

Due to the presence of the bicarbonates, chlorides and sulphates of calcium and magnesium.

Question 16

chemical reaction of D²O with metals

Answer 16

2Na + 2D²O -> 2NaOH + D²

Question 17

chemical reaction of D²O with metallic oxide

Answer 17

Na²O + D²O -> 2NaOD
CaO + D²O -> Ca(OD)²

Question 18

Most abundant element in alkali + alkaline earth metals.

Answer 18

Sodium
Calcium

Question 19

What is diagonal relationship? Cause of diag. relationship.

Answer 19

The similarities in properties of elements present diagonally is called diagonal relationship.

The cause of diagonal relationship is the similarities in properties such as electro negativity, ionization enthalpy, size or charge/radius ratio etc. between the diagonal elements.

Question 20

Radioactive elements in group 1&2 or S block.

Answer 20

Francium, radium.

Question 21

Why Alkali mentals have the lowest ionization enthalpy.

Answer 21

because they have the largest atomic size in their respective periods. The valance electrons in large sized atoms are held loosely by the nucleus and can be lost easily.

Question 22

Why Sodium is kept in kerosene

Answer 22

This is because sodium along with other alkali metals exhibit high chemical reactivity. This is due to their low ionization enthalpy and low enthalpy of atomization. Sodium can react with oxigen in air and water, therefore it is kept in kerosene.

Question 23

why atomic radius of group 2 are smaller than group 1

Answer 23

This is due to the fact that group 2 elements have higher nuclear charge, allowing the electrons to move towards the nucleus.

Question 24

Cement and it’s composition

Answer 24

Cement is a finely ground mixture of calcium silicates and aluminates which set to a hard mass when treated with water.

CaO - 50-60%
MgO - 2-3%
SiO - 20-25%
Fe2O3 - 1-2%
Al2O3 - 5-10%
SO - 1-2%

Question 25

Prep, Property and use of Quick Lime

Answer 25

Calcium oxide / CaO It is prepared on a commercial scale by heating limestone (CaCO3) in a special type of rotary kiln at 1070-1270k CaCO3 -heat-> CaO + CO2 It is used in drying gases and alcohol. On exposure to atmosphere, it absorbs moisture and carbon dioxide.

Question 26

prep, use and prop of NaHCO3

Answer 26

It can be prepared by saturating a solution of sodium carbonate with carbon dioxide. Sodium bicarbonate being less soluble separates out as white crystals. Na2CO3 + H2O + CO2 -> 2NaHCO3 It is used in medicines as an antacid to remove acidity of stomach. It is only sparingly soluble in water.

Question 27

Plaster of Paris prep, prop, use

Answer 27

It is prepared by heating gypsum at 393k. 2(CaSO4. 2H2O) -393k-> (2CaSO4).H2O + 3H2O It is used in dentistry It is a white powder.

Question 28

most abundant element group 13

Answer 28

Aluminium

Question 29

why atomic and ionic radii of group 13 smaller than group 2

Answer 29

This is due to increase in nuclear charge when we move from elements of group 2 to group 13

Question 30

Why are boron halides electron deficient molecules

Answer 30

Boron forms boron halides in which boron has only six electrons around it. Isuch compounds have two electrons less than an octet, therefore it is called electron deficient molecule.

Question 31

Why are boron halides called Lewis Acids.

Answer 31

They have the tendency to accept a pair of electrons to have achieve a stable electronic configuration and therefore, behave as Lewis acids.

Question 32

AlCl3 exists aa a dimer while BaCl3 exists as a monomer. Why?

Answer 32

This is due to the reason that boron atom is very small in size and it cannot accomodate four large halide ions around it to form dimer.

Question 33

most abundant element on group 14

Answer 33

lead

Question 34

Define catenation

Answer 34

The property of forming of bonds with atoms of the same element is called catenation

Question 35

define allotropes

Answer 35

Allotropes are different forms of the same element having different physical properties but almost similar chemical properties.