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The gas bums with a pop sound. From this it is observed that hydrogen gas has been formed due to the reaction between acid and metal.

(c) cell membrane

Cytoplasm is the part of the cell that contains various organelles such as mitochondria, ribosomes, Golgi bodies, etc.

(a) Cytoplasm: It is a fluid that fills the cell and occurs between the plasma membrane and the nucleus. Cell organelles such as mitochondria, ribosomes, Golgi bodies, etc. are suspended in the cytoplasm. The cytoplasm helps in the exchange of materials between cell organelles. 

(b) Nucleus of a cell: Nucleus is the master of the cell. It commands all the functioning of the cell. It is generally located in the center of the cell and is spherical in shape. A membrane called nuclear membrane separates it from cytoplasm. It contains the genetic material DNA and RNA in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. Nucleus contains a dense body called Nucleolus which actually contains chromosomes, the genetic material.

In Biology, the basic unit of which all living things are composed is known as ‘cell’. The ‘cell’ is the smallest structural unit of living matter that is capable of functioning independently. A single cell can be a complete organism in itself, as in bacteria and protozoans. A unicellular organism also captures and digests food, respires, excretes, grows, and reproduces. Similar functions in multi-cellular organisms are carried out by groups of specialized cells which are organized into tissues and organs such as, the higher plants and animals. Hence, ‘cell’ is known as the basic structural and functional unit of life.

Chromosomes are found in the nucleus of a cell. Their function is to carry characteristic features of parent cells to the daughter cell means, from parent to offspring.

(a) ribosome

(c) cell membrane, mitochondria, ribosome, chromosome 

(c) unicellular organisms respire and reproduce. 

(d) chromosome and genes

(c) bacteria and blue-green alga

(d) cytoplasm

A-iii, B-iv; C-ii; D-i

a-cell wall; b-cell membrane; c-cytoplasm; d-cell organelles; e-nucleus; f-chromosomes.

(c) A single cell can perform all the functions in a unicellular organism. 

Elements are Mercury, Iron, Diamond, Nitrogen, Graphite, Hydrogen, Oxygen and chlorine.

Other name for impure substance is Mixture.

Examples: Milk and sea water.

Ice, iron, hydrochloric acid, calcium oxide and mercury are the pure substances.

The answer is (b) AlClg

The least stable hydride of 15^th group elements is (BiH₃).

1. Due to the presence of lone pair on the central atom which is available for donation.

2. NH₃ > PH₃ > ASH₃ > SbH₃ ≥ BiH₃.

In the valence shell of Cl vacant 3d orbitals are available. Hence it can form ClF₃ . But, F has no vacant d orbital to show higher oxidation state and FCl₃ is not possible.

Ionic bond as an extreme case of polar covalent bond – If electronegativity difference between two atoms bonded by a covalent bond is very high, electron can be completely transferred from less electronegative atom to more electronegative atom. This results in formation of oppositely charged ions bonded by electrostatic forces of attraction. This type of linkage is ionic bond.

H₃PO₂ has two P-H bonds but H₃PO₃ has one P-H bond. 

Two H atom of H₃PO₂ are bonded directly with P atom and only one O-H bond is present hence it is monobasic acid.

In H₃PO₂, two H atoms are bonded directly to P atom which imparts reducing character to the acid where as in H₃PO₄ all H atoms are bonded to O- atom.

Basicity is two this is due to two protonated hydrogen in HPO(OH)₂.

This theory was developed by Linus Pauling and it explains the covalent bond formation between two atoms as the interaction or overlap of atomic orbitals. This theory can be described in following points.

(i) A covalent bond is formed when the orbital of one atom is situated in such a way that it overlaps with the orbital of another atom, each of them containing one unpaired electron.

(ii) The atomic orbitals overlap and the overlapped region is occupied by both the electrons. These two electron must have opposite spin.

(iii) As a result of this overlapping, there is maximum electron density between the two atoms. A large part of the binding force of covalent bond results from the attraction of these electrons by the nuclei of both the atoms.

(iv) Atoms maintain their individuality. When the bond is formed, only valence electrons from each bonded atom are involved and the inner atomic orbitals of each atom remain undisturbed.

The simplest example of bond formation by atomic orbital overlap is the formation of H₂ molecule. For two hydrogen atoms (say H₂ and H_b) which are infinitely apart i.e. when there is no a b interaction between them, their potential energy is taken as zero. As the two atoms approach each other, the electron of H_a is attracted by the nucleus of H_b and electron of H_b is similarly attracted by the nucleus of H_a . In an isolated hydrogen atom the electron is attracted by only a a single nucleus, but when two hydrogen atoms are close together, each of the two electrons experiences the attractive pull of two nuclei and energy is lowered. There will also be some repulsion between the two electrons and the two nuclei. At a certain distance between two nuclei these attractive and repulsive forces balance each other. At this distance the two hydrogen atoms form a stable grouping called a hydrogen molecule. This critical distance corresponding to the minimum energy and maximum stability is called the bond length. The energy decreased in this process is called bond energy.

This idea of electron sharing can also be expressed in terms of orbital overlap. When the two atoms are for apart, each electron occupies 1s orbital. As the two atoms approach near to each other, their orbitals overlap partly. The two electrons can now be shared through this overlapped region.

Basicity is one this is due to one protonated hydrogen in H₂PO(OH).

4 H₃PO₃→3H₃PO₄ + PH₃. Because P is in +3 oxd. state, it can go to lower or higher state but in H₃PO₄, P is in +5 sate which can go to lower oxd. State only.

There is a chandnibawadi (stepwell) in our nearby area. The king constructed this bawadi long ago. The water level of the bawadi has decreased due to improper maintenance and the water of the stepwell is also polluted. Now, the bawadi is again being maintained.

We should not store rainwater is True.

khinnibawadi is situated in Jalore

We should not dirty the water of the stepwell and it should be cleaned from time to time.

Household water is supplied to the cities through pipelines.

Electricity is generated by turbine wheel is True.

1. (filtration) 

2. (150) 

3. (circular) 

4. (electricity).

(d) Lakes and dams

We should drink water after filtration or boiling is False.

(a) Banswara

(i) On Mahi river (in Banswara) 

(ii) On Chambal river (in Kota)

The shape of the well is round.

The Medtanibawadi of Jhunjhunu is a very ancient, beautiful and artistic stepwell.

Chambal and Mahi

Chambal river.

Water works department of the government.

(c) Hydrated ferric oxide