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Chemistry Chemistry Some Basic Concepts of Chemistry

For complete combustion of methanol

$C H_{3} O H (1) + \frac{3}{2} O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (I)$

The amount of heat produced as measured by bomb calorimeter is 726 kJmol^-¹ at 27°C. The enthalpy of combustion for the reaction is -x kJ mol^-¹, where x is_________

(Nearest integer)

(Given : R = 8.3 J K^-¹ mol^-¹).

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Payal Gupta

Contributor-Level 10

$C H_{3} O H_{(l)} + \frac{3}{2} O_{2 (g)} \to C O_{2 (g)} + 2 H_{2} O (l)$

$Δ n = - 0.5$

$Δ H = Δ E + Δ n R T = - 726 - 0.5 * \frac{8.3}{1000} * 300 = - 726 - 1.24 = - 727.24 \approx - 727 k J / m o l$

Hence, x = 727 (the nearest integer)

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Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

The moles of methane required to produce 81 g of water after complete combustion is________* 10^-2 mol. (nearest integer)

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Vishal Baghel

Contributor-Level 10

$C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O$

2 moles of water produced by 1 mole of methane

Or 36 gm of water produced by 1 mole of CH₄

$∴$ 81 gm of water produced = $\frac{1 * 81}{36}$ = 2.25 mole of CH₄

Mole of CH4 required = 225 * 10^-2

the nearest integer = 225

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Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

Reaction of [Co(H₂O)₆]²⁺ with excess ammonia and in the presence of oxygen results into a diamagnetic product. Number of electrons present in t_2g-orbitals of the product is_________.

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Vishal Baghel

Contributor-Level 10

${[C o {(H_{2} O)}_{6}]}^{2 +} + N H_{3 (e x c e s s)} \to \underset{D i a m a g n e t i c n a t u r e}{{[C o {(N H_{3})}_{6}]}^{3 +} + 6 H_{2} O}$

$C o^{3 +} \to 3 d^{6} 4 s^{0}$

$\Rightarrow {t_{2 g}}^{6} e g^{0}$ (form of paired electron)

No. of electron in t_2g = 6

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Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

Catalyst A reduces the activation energy for a reaction by 10 kJ mol^-1 at 300K. The ratio of rate constants, $\frac{k_{T}, C a t a l y s e d}{k_{T}, U n c a t a l y s e d} i s e^{x} .$ The value of x is_________. (nearest integer)

[Assume that the pre-exponential factor is same in both the cases. Given R = 8.31 JK^-1 mol^-1]

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Vishal Baghel

Contributor-Level 10

$K_{c a t} = A e^{-} \frac{{(E a)}_{c a t}}{R T} a n d K_{u n c a t} = A e^{-} \frac{{(E a)}_{u n c a t}}{R T}$

$\frac{K_{c a t}}{K_{u n c a t}} = e^{\frac{{(E a)}_{u n c a t} - {(E a)}_{c a t}}{R T}} = e^{\frac{10 * 1000}{8.314 * 300}} = e^{4.009} = e^{x}$

$∴ x = 4$

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Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

Cu(s) + Sn²⁺(0.001M) ® Cu²⁺ (0.01M) + Sn(s)

The Gibbs free energy change for the above reaction at 298 K is x * 10^-1 KJmol^-1. The value of x is __________. (nearest integer)

[Given : $E_{C u^{2 +} / C u}^{Θ}$ 0.34V; $E_{S n^{2 +} / S n}^{Θ}$ =96500 Cmol^-1]

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Vishal Baghel

Contributor-Level 10

cell reaction is ;

$C u (s) + S n_{(a q)}^{2 +} \to C u_{(a q)}^{+ +} + S n_{(s)}$

$Q = \frac{[C u^{+ +}]}{[S n^{+ +}]} = \frac{0.01}{0.001} a n d n = 2$

$E_{c e l l} = E_{c e l l}^{o} - \frac{0.059}{2} l o g \frac{0.01}{0.001}$

$= - 0.48 - \frac{0.059}{2} l o g 10 = - 0.509$

$= 983.33 * 1 0^{- 1} K J / m o l e$

the nearest integer = 983

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a year ago

Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

40% of HI undergoes decomposition to H₂ and I₂ at 300K. $Δ G^{Θ}$ for this decomposition reaction at one atmosphere pressure is_____________J mol^-1 (nearest integer)

(Use R = 8.31 JK^-1 mol^-1; log 2= 0.3010, In 10 = 2.3, log 3 = 0.477)

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Vishal Baghel

Contributor-Level 10

$H l ? \frac{1}{2} H_{2} + \frac{1}{2} l_{2}$

t = eq1 - $\frac{α}{2}$ $\frac{α}{2} [α = 0.4]$

$K p = \frac{{(P_{H_{2}})}^{\frac{1}{2}} * {(P_{l_{2}})}^{\frac{1}{2}}}{P_{H l}} = \frac{{(0.2)}^{\frac{1}{2}} * {(0.2)}^{\frac{1}{2}}}{0.6}$

= $- 8.31 * 300 * 2.3 * l o g (\frac{1}{3}) = 2735 J / m o l$

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a year ago

Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

The osmotic pressure exerted by a solution prepared by dissolving 2.0g of protein of molar mass 60 kg mol^-1 in 200 mL of water at 27°C is_______Pa. (nearest integer)

(Use R = 0.083 L bar mol^-1 K^-1)

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Vishal Baghel

Contributor-Level 10

$π = i * c * R * T = \frac{2 * 0.83 * 300}{60 * 1 0^{3}} = 0.00415 b a r$

= 415 Pa

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a year ago

Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

A fish swimming in water body when taken out from the water body is covered with a film of water of weight 36g. When it is subjected to cooking at 100°C, then the internal energy for vaporization in kJ mol^-1 is_____________. (nearest integer)

[Assume steam to be an ideal gas. Given $Δ_{v a p} H^{Θ}$ for water at 373K and 1 bar is 41.1 kJ mol^-1; R = 8.31 JK^-1mol^-1]

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Vishal Baghel

Contributor-Level 10

Vapourisation of $H_{2} O, H_{2} O_{(l)} \to H_{2} O_{(g)}$

Mole of H₂O= $\frac{36}{18} = 2 m o l$

$Δ E = Δ H - Δ n R T$

$= 41.1 - \frac{1 * 8.31 * 373}{1000} = 38 k J / m o l e$

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a year ago

Chemistry Electrochemistry

Which statement is not true with respect to nitrate ion test?

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Payal Gupta

Contributor-Level 10

Brown ring is formed due to nitrosoferrous sulphate formation.

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a year ago

Chemistry Chemistry NCERT Exemplar Solutions Class 12th Chapter Two

Amongst SF₄, XeF₄, CF₄ and H₂O, the number of species with two lone pairs of electrons is___________.

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Vishal Baghel

Contributor-Level 10

Water has only two lone pair and XeF₄ has two lone pair electron in opposite plane of the central atom.

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