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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

The pH of neutral water at 25°C is 7.0. As the temperature increases, ionisation of water increases, however, the concentration of H⁺ ions and OH^–ions are equal. What will be the pH of pure water at 60°C?

(i) Equal to 7.0

(ii) Greater than 7.0

(iii) Less than 7.0

(iv) Equal to zero

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: As Kw increases Ans: As Kw increases [H+] [OH^-] $>$ 10^-14

[H⁺]= [OH^-]

[H⁺]= [OH^-] [H⁺]_{2 = 110}^-14

[H⁺] $>$ 10^-7

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink. On the basis of this information mark the correct answer.

[Co (H₂O)₆] ³⁺ (aq) + 4Cl^– (aq) ⇌ [CoCl₄]^2– (aq) + 6H₂O (l)

(pink) (blue)

(i) ∆H > 0 for the reaction

(ii) ∆H < 0 for the reaction

(iii) ∆H = 0 for the reaction

(iv) The sign of ∆H cannot be predicte

...more

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (i)

On cooling the mixture reaction moves towards backward direction it means it is an endothermic reaction i.e.,

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

Which of the following statements is incorrect?

(i) In equilibrium mixture of ice and water kept in perfectly insulated flask mass of ice and water does not change with time.

(ii) The intensity of red colour increases when oxalic acid is added to a solution containing iron

(III) nitrate and potassium thiocyanate.

(iii) On addition of catalyst the equilibrium constant value is not affected.

(iv) Equilibrium constant for a reaction with negative ?H value decreases as the temperature increases.

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (ii)

The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
Iron (III) nitrate and potassium thiocyanate react to give deep red coloration.
The reaction is:
Fe³ + aq + SCN⁻↔ [FeSCN]² + aq
yellow deep red
Now, to this solution, if oxalic acid (H₂C₂O₄) is added, then it reacts with Fe³⁺ ions to form the stable complex ion [Fe (C₂O₄)3]³⁻, thus decreasing the concentration of Fe³⁺ ions. In accordance with the Le-Chatelier's principle, the de

...more

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Nine

Give reasons:

(i) Lakes freeze from top towards bottom.

(ii) Ice floats on water.

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Payal Gupta

Contributor-Level 10

(i) During winter, the temperature of lake water keeps on decreasing. Since cold water is heavier, it moves towards the bottom.

(ii) Density of ice is less than that of water that is why it floats on the surface of water.

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

PCl₅, PCl₃ and Cl₂ are at equilibrium at 500K in a closed container and their concentrations are 0.8 * 10^–3 mol L^–1, 1.2 * 10^–3 mol L^–1 and 1.2 * 10^–3 mol L^–1 respectively. The value of Kc for the reaction PCl5 (g) ⇌PCl3 (g) + Cl2 (g) will be

(i) 1.8 * 10³ mol L^–1

(ii) 1.8 * 10^–3

(iii) 1.8 * 10^–3 L mol^–1

(iv) 0.55 * 10⁴

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: The given reaction is :-

PCl5(g)?PCl3(g)+Cl2(g)

KC= $\frac{[P C l 3] [C l 2]}{[P C l 5]}$

=1.2*10⁻³*1.2*10⁻³0.8*10−3 $\frac{[1.2 * 10 - 3 * 1.2 * 10 - 3]}{[0.8 * 10 - 3]}$

=1.8*10⁻³molL⁻¹

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

Which of the following is not a general characteristic of equilibria involving physical processes?

(i) Equilibrium is possible only in a closed system at a given temperature.

(ii) All measurable properties of the system remain constant.

(iii) All the physical processes stop at equilibrium.

(iv) The opposing processes occur at the same rate and there is dynamic but stable condition.

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iii)

A physical equilibrium is having dynamic nature, both forward and reverse process occur at equal rates. Some kind of motion is always present. The individual molecules continuously move from one phase to another.

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

Which of the following is not a general characteristic of equilibria involving physical processes?

(i) Equilibrium is possible only in a closed system at a given temperature.

(ii) All measurable properties of the system remain constant.

(iii) All the physical processes stop at equilibrium.

(iv) The opposing processes occur at the same rate and there is dynamic but stable condition.

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iii)

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Nine

Complete the following equations:

(i) PBS(s)+H₂O₂(aq) →

(ii) CO(g)+H₂(g) →

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Payal Gupta

Contributor-Level 10

This is a short answer type question as classified in NCERT Exemplar

(i) PBS (s)+4H₂O₂ (aq) → PbSO₄ (s)+4H₂O (l)

(ii) CO (g)+2H₂ (g) → CH₃OH (l)

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7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

For the reaction H₂(g) + I₂(g) ⇌ 2HI (g), the standard free energy is ∆Gᶱ > 0. The equilibrium constant (K ) would be __________.

(i) K = 0

(ii) K > 1

(iii) K = 1

(iv) K < 1

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option(iv)

The given chemical reaction is:

H₂(g) + I₂(g) ? 2HI (g)

By, thermodynamical equation of equilibrium,

?G?= -RTlnk>0

Now, R>0 & T>0

⇒ −lnK > 0

⇒ K<1

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New answer posted

7 months ago

Class 11th Chemistry NCERT Exemplar Solutions Class 11th Chapter Seven

We know that the relationship between Kc and Kp is

Kp = Kc (RT)^∆n What would be the value of ∆n for the reaction

NH4Cl (s) ⇌ NH3 (g) + HCl (g)

(i) 1

(ii) 5

(iii) 5

(iv) 2

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Vishal Baghel

Contributor-Level 10

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option(iv)

The relationship between Kp and Kc is

Kp=Kc(RT)Δn

Where ?n = (number of moles of gaseous products) – (number of moles of gaseous reactants)

For the reaction,

NH4C1(s)?NH3(g)+HCl(g)

Δn=2–0=2

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