Class 12th

If a relation $R$ on the set ${1, 2, 3}$ be defined by $R = {(1, 2)}$ , then $R$ is

(A) Reflexive

(B) Transitive

(C) Symmetric

(D) None of these.

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Contributor-Level 10

This is a Objective Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l} G i v e n t h a t : R = {(1, 2)} \\ a R a, ? ? s o i t i s n o t r e f l e x i v e . \\ a R b b u t b R a, s o i t i s n o t s y m m e t y r i c . \\ a R b a n d b R c \Rightarrow a R c w h i c h i s t r u e . \\ S o, R i s t r a n s i t i v e . \\ H e n c e, c o r r e c t a n s w e r i s (b) . \end{array}$

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New answer posted

7 months ago

The maximum number of equivalence relations on the set $A = {1, 2, 3}$ are

(A) 1

(B) 2

(C) 3

(D) 5

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Class 12th Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven

Contributor-Level 10

This is a Objective Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l} H e r e, A = {1, 2, 3} \\ T h e n u m b e r o f e q u i v a l e n c e r e l a t i o n s a r e a s f o l l o w s : \\ R_{1} = {(1, 1), (1, 2), (2, 1), (2, 3), (1, 3)} \\ R_{2} = {(2, 2), (1, 3), (3, 1), (3, 2), (1, 2)} \\ R_{3} = {(3, 3), (1, 2), (2, 3), (1, 3), (3, 2)} \\ H e n c e, c o r r e c t a n s w e r i s (d) \end{array}$

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7 months ago

Assertion : SF₆ cannot be hydrolysed but SF₄can be.

Reason : Six F atoms in SF₆ prevent the attack of H₂O on sulphur atom of SF₆

(i) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.

(ii) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.

(iii) Assertion is correct, but reason is wrong statement.

(iv) Assertion is wrong but reason is correct statement.

(v) Both assertion and reason are wrong statements.

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Contributor-Level 10

This is a assertion and reason answer type question as classified in NCERT Exemplar

Correct option is (i)Here, the S atom is surrounded by 6F atoms, so it's complected for H₂O to attack SF₆, but in case of SF₄, it's surrounded by 4F atoms, so it's to attack H₂O.

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New question posted

7 months ago

Class 12th Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven

The maximum number of equivalence relations on the set $A = {1, 2, 3}$ are

(A) 1

(B) 2

(C) 3

(D) 5

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New answer posted

7 months ago

Assertion : NaCl reacts with concentrated H₂SO₄ to give colourless fumes with pungent smell. But on adding MnO₂ the fumes become greenish yellow.

Reason : MnO₂ oxidises HCl to chlorine gas which is greenish yellow.

(i) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.

(ii) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.

(iii) Assertion is correct, but reason is wrong statement.

(iv) Assertion is wrong but reason is correct statement.

(v) Both assertion and reaso

...more

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Contributor-Level 10

This is a assertion and reason answer type question as classified in NCERT Exemplar

Correct option is (i)

When NaCl reacts with concentrated H₂SO₄, it produces colourless fumes with a pungent smell, but when MnO₂ is added, the fumes turn greenish yellow. MnO₂ oxidizes HCl to chlorine gas, which then turns greenish yellow.

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7 months ago

Consider the non-empty set consisting of children in a family and a relation $R$ defined as $a R b$ if $a$ is the brother of $b$ . Then $R$ is:

(A) Symmetric but not transitive

(B) Transitive but not symmetric

(C) Neither symmetric nor transitive

(D) Both symmetric and transitive.

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Class 12th Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven

Contributor-Level 10

This is a Objective Type Question as classified in NCERT Exemplar

Sol:

$\begin{array}{l} H e r e, a R b \Rightarrow a i s a b r o t h e r o f b . \\ a R a \Rightarrow a i s a b r o t h e r o f a w h i c h i s n o t t r u e . \\ S o, R i s n o t r e f l e x i v e . \\ a R b \Rightarrow a i s a b r o t h e r o f b . \\ b R a \Rightarrow w h i c h i s n o t t r u e b e c a u s e b m a y b e s i s t e r o f a . \\ \Rightarrow a R b \neq b R a \\ S o, R i s n o t s y m m e t r i c . \\ N o w, a R b, b R c \Rightarrow a R c \\ \Rightarrow a i s t h e b r o t h e r o f b a n d b i s t h e b r o t h e r o f c . \\ ∴ a i s a l s o t h e b r o t h e r o f c . \end{array}$

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New answer posted

7 months ago

Assertion : Both rhombic and monoclinic sulphur exist as S₈but oxygen exists as O₂ .

Reason : Oxygen forms pπ – pπ multiple bonds due to small size and small bond length Pπ- Pπ bonding is not possible in sulphur.

(i) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.

(ii) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.

(iii) Assertion is correct, but reason is wrong statement.

(iv) Assertion is wrong but reason is correct statement.

(v) Both assertion and reason are wrong st

...more

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Contributor-Level 10

This is a assertion and reason answer type question as classified in NCERT Exemplar

Correct option is (i)

The rhombic and the monoclinic forms of sulphur exist as S8 . Oxygen forms a p\pi - p\pi multiple bond due to its small size and short bond length, but Pπ- Pπ bonding is not possible because of sulphur's larger atomic size.

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7 months ago

Let $T$ be the set of all triangles in the Euclidean plane, and let a relation $R$ on $T$ be defined as $a R b$ if $a$ is congruent to $b \forall a, b \in T$ . Then $R$ is:

(A) Reflexive but not transitive

(B) Transitive but not symmetric

(C) Equivalence

(D) None of these.

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Class 12th Chemistry NCERT Exemplar Solutions Class 12th Chapter Seven

Contributor-Level 10

This is a Objective Type Question as classified in NCERT Exemplar

Sol: $\begin{array}{l} \end{array}$

$\begin{array}{l} I f a = b \forall a, b \in T \\ t h e n a R a \Rightarrow a ≅ a w h i c h i s t r u e f o r a l l a \in T \\ S o, R i s r e f l e x i v e \\ N o w, a R b a n d b R a . \\ i . e ., a ≅ b a n d b ≅ a w h i c h i s t r u e f o r a l l a \in T \\ R i s s y m m e t r i c . \\ L e t a R b a n d b R c . \\ \Rightarrow a ≅ b a n d b ≅ a \Rightarrow a ≅ c \forall a, b, c \in T \\ S o, R i s t r a n s i t i v e . \\ H e n c e, R i s e q u i v a l e n c e r e l a t i o n . \\ S o, t h e c o r r e c t a n s w e r i s (c) . \end{array}$

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New answer posted

7 months ago

Assertion : HI cannot be prepared by the reaction of KI with concentrated H₂SO₄

Reason : HI has lowest H–X bond strength among halogen acids

(i) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.

(ii) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.

(iii) Assertion is correct, but reason is wrong statement.

(iv) Assertion is wrong but reason is correct statement.

(v) Both assertion and reason are wrong statements.

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Contributor-Level 10

This is a assertion and reason answer type question as classified in NCERT Exemplar

Correct option is (ii)

Because H₂SO₄ is a stronger oxidising agent and HI is a stronger reducing agent, H₂SO₄ oxidizes and is reduced to SO₂.

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New answer posted

7 months ago