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6 months ago

Class 12th Organic Chemistry - Some Basic Principles and Tech

In the estimation of bromine, 0.5g of an organic compound gave 0.40g of silver bromide. The percentage of bromine in the given compound is____________% (Nearest integer)

(Relative atomic masses of Ag and Br are 18 u and 80 u, respectively).

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Payal Gupta

Contributor-Level 10

Organic compound → AgBr (s)

0.5 g 0.40 g

Here; Moles of Br in organic compound = Moles of Br in Ag Br

= Moles of AgBr

= $\frac{0.40}{188} m o l$

Mass of Br in organic compound = $\frac{0.4}{188} * 80 g$

$\begin{array}{l} % o f B r = \frac{0.4 * 80}{188 * 0.5} * 100 % \\ = 34 % \end{array}$

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6 months ago

Class 12th Coordination Compounds

Number of complexes which will exhibit synergic bonding amongst $[C r {(C O)}_{6}], [M n {(C O)}_{5}]$ and $[M n_{2} {(C O)}_{10}]$ is_______________.

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Payal Gupta

Contributor-Level 10

All metal carbonyls have synergic bonds.

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6 months ago

Class 12th Physics NCERT Exemplar Solutions Class 12th Chapter Eleven

A pressure-pump has a horizontal tube of cross sectional area 10cm2 for the outflow of water at a speed of 20 m/s. The force exerted on the vertical wall just in front of the tube which stops water horizontally flowing out of the tube, is:

[given : density of water = 1000 kg/m³]

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Vishal Baghel

Contributor-Level 10

A = 10 cm², V = 20 m/s

$F = \frac{d p}{d t} = ρ A V^{2} = 1 0^{3} * 10 * 1 0^{- 4} * 400$

= 400 N.

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6 months ago

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

For a first order reaction A→B, the rate constant, k = 5.5 * 10^-¹⁴s^-¹. The time required for 67% completion of reaction is x * 10^-¹ times the half life of reaction. The value of x is ________ (Nearest integer)

(Given : log 3 = 0.4771)

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Payal Gupta

Contributor-Level 10

Rate constant, k = 5.5 * 10^-14 s^-1.

$t = \frac{2.303}{k} l o g \frac{{[R]}_{0}}{[R]}$

= $\frac{2.303}{k} l o g 3 - (i)$

$t_{50 %} = \frac{2.303}{k} l o g 2 - (i i)$

From (i) & (ii)

$\frac{t_{67 %}}{t_{50 %}} = \frac{l o g 3}{l o g 2}$

= 1.58 t_50%

So; t_67%is 15.8 * 10^-1 times half life.

X = 16 (the nearest integer)

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6 months ago

Class 12th Physics NCERT Exemplar Solutions Class 12th Chapter Eleven

At time t = 0 a particle starts travelling from a height $7 \hat{z} c m$ in a plane keeping z coordinate constant. At any instant of time it's position along the $\hat{x} a n d \hat{y}$ directions are defined as 3t and 5t3 respectively. At t = 1s acceleration of the particle will be

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Vishal Baghel

Contributor-Level 10

x = 3t y = 5t³

$V_{x} = \frac{d x}{d t} = 3 V_{y} = \frac{d y}{d t} = 15 t^{2}$

$a_{x} = \frac{d V_{x}}{d t} = 0 a_{y} = \frac{d V_{y}}{d t} = 30 t$

$\vec{a} = 30 t \hat{j}$

at t = 1 sec, $\vec{a} = 30 \hat{j}$

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6 months ago

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

The quantity of electricity in Faraday needed to reduce 1 mol of $C r_{2} O_{7}^{2 -}$ to Cr³⁺ is________.

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Payal Gupta

Contributor-Level 10

$C r_{2} O_{7}^{2 -} + 6 e^{-} + 14 H^{+} \to 2 C r^{3 +} + 7 H_{2} O$

Here, 6F electricity is required to reduce 1 mol $C r_{2} O_{7}^{2 -}$ to Cr³⁺.

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6 months ago

Class 12th Physics NCERT Exemplar Solutions Class 12th Chapter Eleven

Consider the efficiency of carnot's engine is given by $η = \frac{α β}{s i n θ} l o g e \frac{β x}{k T},$ where and are constants. If T is temperature, k is Boltzmann constant, is angular displacement and x has the dimensions of length. Then, choose the incorrect option

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Vishal Baghel

Contributor-Level 10

Efficiency $η = \frac{α B}{s i n θ} l o g_{e} \frac{B x}{k T} α, B \to c o n s t a n t s$

As, energy $= \frac{1}{2} k T \Rightarrow$ Dimension of Bx = Dimension of energy

So Dimension as of B = Dimension of 'F'

Dimension of F1

Dimension of $(\frac{1}{α}) x =$ Dimension of energy

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6 months ago

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

The solubility product of a sparingly soluble salt A₂X₃ is 1.1 * 10^-²³. If specific conductance of the solution is 3 * 10^-¹, the limiting molar conductivity of the solution is x * 10^-³ S m² mol^-¹. The value of x is_________.

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Payal Gupta

Contributor-Level 10

Using ; k_sp = 108 S⁵

1.1 * 10^-23 = 108 S⁵

S = ${(\frac{110}{108} * 1 0^{- 25})}^{1 / 5} M \approx 1 0^{- 5} M$

Specific conductance,

$λ_{m}^{0} = \frac{κ}{5 * 1000} S m^{2} m o l^{- 1}$

= 3 * 10^-3 Sm² mol^-1

So; x = 3

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6 months ago

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

The vapour pressure of two volatile liquid A and B at 25°C are 50 Torr and 100 Torr, respectively. If the liquid mixture contains 0.3 mole fraction of A, then the mole fraction of liquid B in the vapour phase is $\frac{x}{17} .$ The value of x is____________.

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Payal Gupta

Contributor-Level 10

$P_{A}^{0} = 50 t o r r$

$P_{B}^{0} = 100 t o r r$

Mole fraction of A in liquid phase, x_A = 0.3

Mole fraction of B in liquid phase, x_B = 0.7

Now; $P_{A} = P_{A}^{0} x_{A}$

$P_{B} = P_{B}^{0} x_{B}$

= 100 * 0.7 = 70 torr

Mole fraction of B in vapour phase, $y_{B} = \frac{P_{B}}{P_{A} + P_{B}} = \frac{70}{85}$

$\frac{70}{85} = \frac{x}{17}$

X = 14

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6 months ago

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

4.0 L of an ideal gas is allowed to expand isothermally into vacuum until the total volume is 20L. The amount of heat absorbed in this expansion is _________L atm.

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Payal Gupta

Contributor-Level 10

For expansion in vacuum, workdone, w = 0

For isothermal process, $Δ U = 0$

According to first law of thermodynamics,

$\begin{array}{l} Δ U = q + w \\ q = 0 \end{array}$

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