cbse 11th chemistry | Online Objective Test

Q1. Self-ionization of water is called

A. Auto-protolysis

B. Hydrolysis Reaction

C. Redox Reactions

D. Water-gas shift reaction

Answer : Option A
Explaination / Solution:

In auto-protolysis a proton is transferred between two identical molecules, one of which acts as a Bronsted acid, releasing a proton which is accepted by the other molecule acting as a Bronsted base.

Auto-protolysis is also called the self-ionization. Auto-protolysis of water is a reaction in which self-ionization of water molecules takes place to produce hydronium ion (H3O+) and hydroxide ion (OH-).

$2 H_{2} O ⇌ H_{3} O^{+} + O H^{-}$

Thermodynamics Prepare / Learn

Q2. Which of the following statements is correct?

A. The presence of reacting species in a covered beaker is an example of open system

B. The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.

C. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.

D. The presence of reactants in a closed vessel made up of copper is an example of a closed system.

Answer : Option D
Explaination / Solution:

It will be a closed system.

Chemical Bonding and Molecular Structure Prepare / Learn

Q3. For a stable molecule the value of bond order must be

A. negative

B. positive

C. zero

D. there is no relationship between stability and bond order

Answer : Option B
Explaination / Solution:

Bond order∝Stability Hence, for a stable molecule the value of bond order must be positive. When bond order is zero and negative the molecule will not exist.

The s-Block Elements Prepare / Learn

Q4. The alkali metals are low melting. Which of the following alkali metal is expected? to melt if the room temperature rises to

3 0^{\circ} C ?

A. Rb

B. K

C. Cs

D. Na

Answer : Option C
Explaination / Solution:

Cs has very low melting point (

30^{O}

)

Organic Chemistry Some Basic Principles and Techniques Prepare / Learn

Q5.

For testing halogens in an organic compound with

AgN O_{3}

solution, sodium extract (Lassaigne’s test) is acidified with dilute

HN O_{3} .

What will happen if a student acidifies the extract with dilute

H_{2} S O_{4}

in place of dilute HNO3?

A. green ppt. of

A g_{2} S O_{4}

will be formed

S O_{2}

will be formed

C. White ppt. of

A g_{2} S

will be formed

D. white ppt. of

A g_{2} S O_{4}

is formed.

Answer : Option D
Explaination / Solution:

white precipitate of

A g_{2} S O_{4}

is formed.

States of Matter Prepare / Learn

Q6. Which of the following property of water can be used to explain the spherical shape of rain droplets?

A. pressure

B. viscosity

C. surface tension

D. critical phenomena

Answer : Option C
Explaination / Solution:

surface Tension is used.

Some Basic Concepts of Chemistry Prepare / Learn

Q7. SI unit of density is

A. kg

m^{- 2}

B. kg

^{- 1} m^{3}

C. kg

m^{3}

D. kg

m^{3}

Answer : Option D
Explaination / Solution:

Since, density

= mass / volume ;

and SI unit of mass is kg and that of volume is $m^{3}$

$∴$ using these SI units the unit of density is derived through dimensional analysis :

density = mass / volume

= kg / m3

or, = kg m-3

Hydrocarbons Prepare / Learn

Q8. The reagent(s) for the following conversion, is/are

A. Zn/CH3OH

B. aqueous KOH followed by

NaN H_{2}

C. Alcoholic KOH followed by

N a N H_{2}

D. alcoholic KOH

Answer : Option C
Explaination / Solution:

Alcoholic KOH followed by

N a N H_{2}

is used. Both are bases.

N a N H_{2}

is better base than alc.KOH.

Equilibrium Prepare / Learn

Q9. It has been found that the pH of a 0.01M solution of an organic acid is 4.15.Calculate the concentration of the anion, the ionization constant of the acid and its

p K_{a}

K_{a} = 5 .0 1 X

10^{- 7}

[A^{-}]

= 7 .0 8 X

10^{- 5}

and

p K_{a} = 5.3007

K_{a} = 5 .0 1 X

10^{- 7}

[A^{-}]

= 7 . 99 X

10^{- 5}

and

p K_{a} = 7.5009

K_{a} = 5 .0 1 X

10^{- 7}

[A^{-}]

= 7 . 39 X

10^{- 5}

and

p K_{a} = 6.3001

K_{a} = 5 .0 1 X

10^{- 7}

[A^{-}]

= 7 . 39 X

10^{- 5}

and

p K_{a} = 6.3001

Answer : Option D
Explaination / Solution:

Ka =

C α^{2}

and pH=-log(Cα) and pKa=-logKa

Redox Reactions Prepare / Learn

Q10. Consider the elements: Cs, Ne, I and F. Identify the element(s) that exhibits only Positive oxidation state

A. I

B. Cs and I

C. Cs

D. Ne

Answer : Option C
Explaination / Solution:

Cs is alkali metal so will show positive oxidation state of +1.

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