Question
Read the following and answer any three questions from (i) to (iv).As neutral atom carbon has electronic configuration $\text{K}\ \ \ \text{L}\\2\ \ \ \ 4$ To gain inert gas configuration carbon can either donate 4 valence electrons (helium gas configuration) or gain 4 electrons (neon gas configuration), but it cannot do so. To acquire inert gas configuration carbon can only share its 4 valence electrons with other atoms forming covalent bonds. A covalent bond can be defined as a chemical bond formed between two atoms by mutual sharing of valence electrons so that each atom acquires the stable electronic configuration of the nearest noble gas. The concept of covalent bonds was given by Langmuir and Lewis to explain bonding in non-ionic compounds. The covalent bonds are of three types. If each atom contributes one electron, the covalent bond formed is called a single covalent bond and is represented by a single line (-) and if each atom contributes two electrons, the covalent bond formed is called a double bond and is represented by a double line (=) and if each atom contributes three electrons, the covalent bond formed is called a triple bond and is represented by a triple line $(\equiv).$
  1. Which compounds do not contain a double bond?
     
  2. Write compounds which contains a triple bond?
     
  3. Which molecules has all its atoms joined together by double covalent bond? Give two example.

    OR
  4. A) Langmuir and Lewis has given which concept?

    B) Explain three types of covalent bonds?

Answer

  1. (b) II and III only
Explanation:
Both $NH_3$ and HCI have single bonds.
  1. (a) $N_2$
Explanation:
$\text{N}\equiv\text{N}$
  1. (a) Single.
  1. (c) Carbon dioxide.
  1. (c)

Explanation:
In chlorine molecule, both chlorine atoms contribute one electron and thus share single electron pair to form single covalent bond. As shared pair is shared by both atoms, they acquire inert gas configuration of argon atom in valence shell.

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Riya wants to ind out how metal conducts heat.
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Riya heats one end of the copper rod with a lame.

Image
1. Which nail will fall last?
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Which of the above four lenses will she require to correct the defect in her vision? Why ?
or
(iv) Natasha places an object on the principal axis of above given lens A. One end of this object coincides with the focus $F$ and the other end with $2 F$. What will be the nature of the image formed by the lens on the other side?

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Image
4. What can Medha conclude from her activity?
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What is the technique known as?

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An insulated copper wire wound on a cylindrical cardboard tube such that its length is greater than its diameter is called a solenoid. When an electric current is passed through the solenoid, it produces a magnetic field around it. The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet. The field lines inside the solenoid are in the form of parallel straight lines. The strong magnetic field produced inside a current-carrying solenoid can be used to magnetize a piece of a magnetic material like soft iron when placed inside the solenoid. The strength of the magnetic field produced by a current-carrying solenoid is directly proportional to the number of turns and strength of the current in the solenoid.

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(a) What would be the strength of the magnetic field inside a long current-carrying straight solenoid?
(b) Which end is north and which end is south pole when current flows through a solenoid?
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A soft iron bar is enclosed by a coil of insulated copper wire as shown in the figure. When the plug of the
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The diagram shows how a human eye sees a candle.

Image
1. What is X?<
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B. Pupil
C. Retina
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A. Age of the person
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C. ocal length of the lens
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Image
6. Which part of the eye controls the size of the pupil?
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Circle ‘Yes’ or ‘No’ to mark your responses.

Is this statement correct?

Yes or No

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Yes/No

His eyeballs are elongated.

Yes/No

All chromosomes in human cells are found in pairs.

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Read the following and answer any three questions from (i) to (iv).An insulated copper wire wound on a cylindrical cardboard tube such that its length is greater than its diameter is called a solenoid. When an electric current is passed through the solenoid, it produces a magnetic field around it. The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet. The field tines inside the solenoid are in the form of parallel straight tines. The strong magnetic field produced inside a current-carrying solenoid can be used to magnetise a piece of magnetic material, like soft iron, when placed inside the solenoid. The strength of magnetic field produced by a current carrying solenoid is directly proportional to the number of turns and strength of current in the solenoid.
  1. The strength of magnetic field inside a long current-carrying straight solenoid is called?
     
  2. The north-south polarities of an electromagnet can be found easily by using which rule?
     
  3. Define a solenoid?
     
  4. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is double and the number of turns per cm is halved, then new value of magnetic field will be?