Class 12th

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In acidic solution

$3 \overset{+ 6}{M n} O_{4}^{2 -} + 4 H^{+} \to 2 \overset{+ 7}{M n} O_{4}^{-} + \overset{+ 4}{M n} O_{2} + 2 H_{2} O$

Difference in oxidation state of Mn is product

= 7 – 4 = 3

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Class 12th Chemistry

(a) Baryte (b) Galena (c) Zinc blende and (d) Copper pyrites. How many of these minerals are sulphide based?

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Contributor-Level 10

Baryte – BaSO₄ [Sulphate based ore]

Galena – PbS

Zinc blende – ZnS

Copper pyrite – CuFeS₂

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Let S = ${\sqrt[]{n} : 1 \leq n \leq 50 a n d n i s o d d}$ .

Let $a \in S a n d A = [\begin{matrix} 1 & 0 & a \\ - 1 & 1 & 0 \\ - a & 0 & 1 \end{matrix}] .$ If $\sum_{a \in S}^{} d e t (a d j A)$ = 100l, then l is equal to :

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Contributor-Level 10

S = ${\sqrt[]{n} : 1 \leq n \leq 50 & n = o d d}$

= ${\sqrt[]{1}, \sqrt[]{3}, \sqrt[]{5}, . . . . . ., \sqrt[]{49} (25 t e r m s)}$

$| A | = | \begin{matrix} 1 & 0 & 4 \\ - 1 & 1 & 0 \\ - a & 0 & 1 \end{matrix} |$ = 1 + a²

^{$∴ \sum_{a \in S}^{} d e t (a d j A) = 100 λ \Rightarrow \sum {(1 + a^{2})}^{2} = 100 λ \Rightarrow λ = 221$}

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Class 12th Chemistry

When 200mL of 0.2 M acetic acid is shaken with 0.6g of wood charcoal, the final concentration of acetic acid after adsorption is 0.1M. The mass of acetic acid adsorbed per gram of carbon is ______________ g.

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Class 12th Chemistry Electrochemistry

Contributor-Level 10

Number of moles of CH₃COOH Adsorbed on 0.6 gm wood charcoal.

$= (0.2 * 200) * 1 0^{- 3} - (0.1 * 200) * 1 0^{- 3}$

= 20 * 10^-3 moles

Mass of CH₃COOH absorbed = 20 * 10^-3 * 60 = 1.2 gm

Mass of CH₃COOH adsorbed per gram = $\frac{1.2}{0.6} = 2 g$ of charcoal.

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The resistance of a conductivity cell containing 0.01 MKCl solution at 298K is $1750 Ω$ . If is 0.152 * 10^-3 cm^-1, then the cell constant of the conductivity cell _________ * 10^-3 cm^-1.

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Class 12th Chemistry Solutions

Contributor-Level 10

$K = \frac{1}{R} * c e l l c o n s t a n t$

= 0.152 * 10^-3 * 1750

= 266 * 10^-3 cm^-1

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A Company dissolves 'x' amount of CO₂ at 298K in 1 litre of water to prepare soda water X = _________________ * 10^-3 g. (nearest integer)

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Contributor-Level 10

According to Henry's law

$P_{G a s} = K_{H} * x_{G a s}$

$= 0.835 = 1.67 * 1 0^{3} * [\frac{n_{C O_{2}}}{n_{C O_{2}} + 55.5}]$

As $n_{C O_{2}} < < 55.5$

$\Rightarrow n_{C O_{2}} = 27.78 * 1 0^{- 3} m o l e s$

Mass of CO₂ gas = $n_{C O_{2}} * (M M) C O_{2}$

= 1222 * 10^-3gm

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The number of values of a for which the system of equations :

x + y + z = a

ax + 2ay + 3z = -1

x + 3ay + 5z = 4

is inconsistent, is

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For inconsistent, $Δ = 0, | \begin{matrix} 1 & 1 & 1 \\ α & 2 a & 3 \\ 1 & 3 α & 5 \end{matrix} | = 0$

a = 1

$∴ Δ_{1} = | \begin{matrix} 1 & 1 & 1 \\ - 1 & 2 & 3 \\ 4 & 3 & 5 \end{matrix} | = 1 (1) + 1 (12 + 5) + 1 (- 3 - 8) = 7 \neq 0$

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Bag A contains 2 white, 1 black and 3 red balls and bag B contains 3 black, 2 red and n white balls. One bag is chosen at random and 2 balls drawn from it at random are found to be 1 red and 1 black. If the probability that both balls come from Bag A is $\frac{6}{11},$ then n is equal to ________.

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Contributor-Level 10

$\frac{6}{11}$ = Required probability

After solving, we get n = 4

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The surface area of a balloon of spherical shape being inflated increases at a constant rate. If initially, the radius of balloon is 3 units and after 5 seconds, it becomes 7 units, then its radius after 9 seconds is :

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Contributor-Level 10

Surface area, S = 4pr²

$? \frac{d s}{d t} = 4 ? . 2 r \frac{d r}{d t} = 8 ? \frac{d r}{d t} = c o n s t a n t = k (s a y)$

$? \frac{d s}{d t} = k ? s = k t + c$

$? 4 ? r^{2} = k t + c$

Initially t = 0, r = 3

c = 36 p

When t = 5, r = 7, k = 32p

When t = 9, r = r, r = 9

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In an examination, there are 1- true-false type questions. Out of 10, at student can guess the answer of 4 questions correctly with probability $\frac{3}{4}$ and the remaining 6 questions correctly with probability $\frac{1}{4}$ . If the probability that the student guesses the answer of exactly 8 questions correctly out of 10 is $\frac{27 k}{4^{10}},$ then k is equal to

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