3.Case Study Question (11 to 15).pdf

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CASE STUDY QUESTION 11

Read the following and answer any four questions from (i) to (v)

Whenever a solution has a pH of less than 7, it will be

an acidic solution. For example, a solution having a pH

of 4 will be acidic in nature (or it will be an acid).

Please note that more acidic a solution is, the lower

will be its pH. For example, a solution of pH 1 is much

more acidic than another solution of pH 4. In other

words, a solution of pH 1 will be a much more stronger

acid than another acid having pH 4 (see the figure). The

solutions having pH of 0, 1, 2 and 3 are usually

considered to be strong acids. And the solutions having

pH of 4, 5 and 6 are considered to be weak acid

solutions. It is clear that the acidity of a substance is

related to its pH. Strongly acidic substances have a very

low pH. In fact, lower the pH, the stronger the acid.

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(i) A solution turns red litmus blue. Its pH is likely to be :

(a) 1 (b) 4 (c) 5 (d) 10

(ii) The pH values of six solutions A to F are given below :

A = 0, B = 11, C = 6, D = 3, E = 13, F = 8

Which of the above solutions are acids

(a) A, C, D (b) A, B, C (c) A, C, D, F (d) A, C, D, E

Ans: (a) A, C, D

Ans: (d) 10

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(iii) Fresh milk has a pH of 6. When milk changes into curd, the pH value will :

(a) become 7 (b) become less than 6

Ans: (b) become less than 6

(iv) The pH values of three acids A, B and C having equal molar concentrations

are 5.0, 2.8 and 3.5 respectively.

Arrange these acids in order of the increasing acid strengths.

(a) A, C, B (b) B, C, A (c) A, B, C (d) C, B, A

"Lesser the pH, stronger the acid.“

Considering the above statement, the order of increasing acidic strength is

A < C < B

Ans: (a) A, C, B

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pH = 1 will turn the scale red. It is a strong acid.

(v)A beaker of concentrated hydrochloric acid has a pH of 1. What colour will full

range universal indicator turn if it is added to this beaker ?

(a) red (b) blue (c) pink (d) no change in colour

Ans: (a) red

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CASE STUDY QUESTION 12

Read the following and answer any four questions from 20(i) to 20(v).

Reproduction is a process by which living

organisms are able to produce young ones of their

new kind. Living organisms reproduce by two

ways - asexual reproduction and sexual

reproduction. Asexual reproduction involves the

production of an offspring from a single parent

without the fusion of gametes. This mostly occurs

in unicellular organisms, some plants and certain

multicellular organisms. There are various types of

asexual reproduction.

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(i) The type of reproduction shown in the figure is

(a) budding (b) fragmentation (c) regeneration (d) fission.

Regeneration is the process by which small cut parts of body organism grow

to form whole new organisms.

Ans: (c) regeneration

(ii) Which of the following is correct example of the process shown in the given figure?

(a) Hydra (b) Planaria (c) Amoeba (d) Both (a) and (b)

Simple animals like Hydra and Planaria can be cut into any number of pieces and

each piece grows into a complete organism by regeneration.

Ans: (d) Both (a) and (b)

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(iii) A feature of reproduction that is common to Amoeba, yeast and bacteria is that

(a) they are all unicellular (b) they are all multicellular

(iv) Asexual reproduction is

(a) a fusion of specialised cells

(b) a method by which all types of organism reproduce

(d) a method in which more than one parent are involved.

Ans: (d) they reproduce asexually.

In asexual reproduction, the young one receives all its genes from one

parent, so offspring produced are genetically identical to the parents.

Ans: (c) a method producing genetically identical offspring

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(v) From the given list of organisms, those which reproduce by the asexual method are:

(i) Aspergillus (ii) Dog (iii) Papaya (iv) Paramecium

(a) (i) and (ii) (b) (ii) and (iii)

Aspergillus and Paramecium reproduce by spore formation and fission

respectively. All these are methods of asexual reproduction. Dog and papaya

reproduces through sexual methods.

Ans: (c) (i) and (iv)

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CASE STUDY QUESTION 13

Read the following and answer any four questions from (i) to (v)

A group of students measured the pH of some substances they found in their homes.

Their results are given in the following table :

Substance pH Substance pH

Apples 3.0 Vinegar 3.0

Salt 7.0 Lemon juice 2.5

Baking soda 8.5 Washing soda 11.5

Sugar 7.0 Milk 6.5

Black coffee 5.0 Household ammonia 12.0

Toothpaste 9.0

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(a) Which solution is the most acidic?

(i) Apples (ii) Vinegar

(iii) Lemon Juice (iv) Black Coffee

Ans: (iii) Lemon juice

(b) Which solution is the most alkaline ?

(i) Household ammonia

(ii) Washing soda

(iii) Baking soda

(iv) Toothpaste

Ans: (i) Household ammonia

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(i) Salt

(ii) Sugar

(iii) Milk

(iv) Both (i) and (ii)

Ans: (iv) Both (i) and (ii)

(iv) What will be the litmus test if the solution is basic?

(a) Red litmus will turn to blue

(b) Blue litmus will turn to red

(d) It will change into orange pink.

Ans: (a) Red litmus will turn to blue

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(v) Arrange the following in order of the increasing basic strengths.

Baking soda, Toothpaste, Household ammonia, Washing soda

(a) Baking soda, Toothpaste, Household ammonia, Washing soda

(b) Baking soda, Toothpaste, Washing soda, Household ammonia

(d) Baking soda, Household ammonia, Toothpaste, Washing soda

Higher the pH, the stronger the base

Ans: (b) Baking soda, Toothpaste, Washing soda, Household ammonia

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CASE STUDY QUESTION 14

Read the following and answer any four questions from (i) to (v)

In household electric circuits, the mains supply is delivered to our homes using three

core cable as shown here. The cable consists of three wires, live wire, neutral wire and

earth wire. The live wire is at potential difference of 220 V for the domestic supply

and the potential difference between live and neutral wire is 220 volts. The live wire is

connected to electric meter through a fuse or a circuit breaker of higher rating. The

neutral wire is connected directly to the electric meter.

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(i) Potential difference between live and neutral wire is

(a) 1000 V (b) 100 V (c) 500 V (d) 220 V

(ii) Switches are connected in household circuit with which wire?

(a) Earth wire (b) Neutral wire (c) Live wire (d) None of these

Ans: (d) 220 V

The potential different between live and neutral wire is 220 Volts.

Ans: (c) Live wire

Switches are connected in the live wire because when the switch is in the off

position, no point of the connected electrical appliance will be at higher

potential (220 V).

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(iii) What is usual current rating of the fuse wire in the line if electric iron, geysers,

room heater etc. are in use?

(a) 15 A (b) 5 A (c) 10 A (d) 25 A

(iv) For all electrical appliances which property of circuit is recommended?

(a) Earthing (b) Neutralising

Ans: (a) 15 A

A fuse of rating 15 A is usually used for appliance electric iron, geysers and room

heater etc.

Ans: (a) Earthing

The earthing of any electrical appliance is done to protect the user from any

accidental electrical shock due to leakage of current.

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(v) Home circuit is connected in parallel because

(a) in parallel circuit resistance is maximum

(b) in parallel circuit if one device is damaged, then it does not affect other devices

(d) none of these.

Ans: (b) in parallel circuit if one device is damaged, then it does not affect

other devices

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CASE STUDY QUESTION 15

Read the following and answer any four questions from (i) to (v)

Light is a form of energy that produces

in us the sensation of sight. Reflection

of light is the phenomenon of bouncing

back of light in the same medium on

striking the surface of any object. The

two laws of reflection are the incident

ray, the reflected ray and the normal (at

the point of incidence), all lie in the

same plane and the angle of reflection

(r) is always equal to the angle of

incidence (i). Refraction of light is the

phenomenon of change in the path of

light in going from one medium to

another.

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A ray of light passes from a medium of water to that of air. Light ray will be refracted

at the junction separating the two media. Since it passes from a medium of a higher

refractive index to that having a lower refractive index, the refracted light ray bends

away from the normal.

At a specific angle of incidence, the incident ray of light is refracted in such a way that

it passes along the surface of the water. This particular angle of incidence is called the

critical angle. Here the angle of refraction is 90 degrees.

When the angle of incidence is greater than the critical angle, the incident ray is

reflected back to the medium. We call this phenomenon total internal reflection.

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Mirage is an optical illusion which is responsible for the appearance of the

water layer at short distances in a desert or on the road. Mirage is an

example of total internal reflection which occurs due to atmospheric

refraction.

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(i) Mirage is caused due to

(a) total Internal Reflection of light by the various layers of air

(b) illusion of the presence of water

(d) during sunny days when driving on a roadway

Ans: (a) total Internal Reflection of light by the various layers of air

(ii) What is mirage?

(a) Depends on the position of object

(b) Mirror is concave and the lens is convex

(d) Optical illusion caused due to total Internal Reflection

Ans: (d) Optical illusion caused due to total Internal Reflection

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(iii) What is the condition for total internal reflection?

(a) Angle of incidence is less than to critical angle

(b) Angle of incidence is equal to critical angle

(d) None of these

Ans: (c) Angle of incidence is greater than to critical angle

(iv) Mirage is observed mainly during ______ days.

(a) Sunny (b) Winter (c) Spring (d) Hot

Ans: (a) Sunny

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(v) How a mirage is formed?

(a) Between focus and centre of curvature

(b) Is formed away from the normal

(d) Is reflected along the same path

non-uniform medium