Ncert Solutions Chemistry Class 12th

In the below reaction, 5g of toluene is converted into benzaldehyde with 92% yield. The amount of benzaldehyde produced is____________* 10^-² g. (Nearest integer)

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No. of moles = $\frac{5}{92} (t o l u e n e)$

Moles of benzaldehyde = $\frac{5}{92} * \frac{92}{100} = 5 * 1 0^{- 2}$

Mass of benzaldehyde = 5 * 10^-2 *106 = 5.3 gm

= 530 * 10^-2 gm

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The spin only magnetic moment of the complex present in Fehling's reagent is __________B.M.

(Nearest Integer)

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Fehling's solution is a complex of $C u^{2 +}, C u^{2 +} = 3 d^{9}$

No. of unpaired e^- = 1

MM = $\sqrt[]{1 (1 + 2)} = \sqrt[]{3} = 1.73 B M$

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The oxidation state of manganese in the product obtained in a reaction of potassium permanganate and hydrogen peroxide in basic medium is___________.

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$2 K M n O_{4} + 3 H_{2} O_{2} \to_{}^{B a s i c m e d i u m} 2 M n O_{2} + 3 O_{2} + 2 H_{2} O + 2 K O H$

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Among the following ores Bauxite, Siderite, Cuprite, Calamine, Haematite, Kaolinite, Malachite, Magnetite, Sphalerite, Limonite, Cryolite, the number of principal ores if iron is ___________.

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Bauxite = AlOx (OH)_3-2x (where O < x < 1)

Siderite = FeCO₃

Cuprite = Cu₂O

Calamine = ZnCO₃

Haemetite = Fe₂O₃

Kaolinite = Al₂ (OH)₄Si₂O₅

Malachite = CuCO₃ Cu (OH)₂

Magneite = Fe₃O₄

Sphalerite = ZnS

Limonite = Fe₂O₃.3H₂O

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In the following reaction

The % yield for reaction I is 60% and that of reaction II is 50%. The overall yield of the complete reaction is___________% [Nearest integer]

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Let initial moles of reactant taken = n. Total moles obtained for benzene sulphonic acid = 0.6 n (with % yield = 60%)

Moles of benzene sulphonic acid before reaction II = 0.6n

Moles obtained for phenol (with % yield 50%) = 0.6 * 0.5 n = 0.3 n

So, overall % age yield of complete reaction = $\frac{0.3 n}{n} * 100 = 30 %$

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Optical activity of an enantiomeric mixture is + 12.6° and the specific rotation of (+) isomer is +30°. The optical purity is_____________%

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$% O p t i c a l p u r i t y = \frac{O b s e r v e d r o t a t i o n o f m i x t u r e * 100}{r o t a t i o n o f p u r e e n a u t i o m e r}$

$= \frac{+ 12.6}{+ 30} * 100 = 42 %$

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In the titration of KMnO₄ and oxalic acid in acidic medium, the change in oxidation number of carbon at the end point is____________.

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$2 K M n O_{4} + 5 H_{2} {\overset{+ 3}{C}}_{2} O_{4} + 3 H_{2} S O_{4} (d i l) \to K_{2} S O_{4} + 2 M n S O_{4} + 10 C {\overset{+ 4}{O}}_{2} + 8 H_{2} O$

Oxidation state of carbon changes from +3 to +4

$∴$ change in O. S is 1

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At 310 K, the solubility of CaF₂ in water is 2.34 * 10^-3 g/ 100 mL. The solubility product of CaF₂ is ____________* 10^-8 (mol/L)³. (Give molar mass : CaF₂ = 78 gmol^-1)

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Solubility of CaF₂ = S mol/L

$S = \frac{2.34 * 1 0^{- 3}}{0.1 * 78} = \frac{2.34}{78} * 1 0^{- 2} = 3 * 1 0^{- 4} m o l / L$

$K_{s p} (C a F_{2}) = 4 S^{3} = 4 {(3 * 1 0^{- 4})}^{3} = 108 * 1 0^{- 12}$

= 0.0108 * 10^-8 (mol/L)³

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20 mL of 0.02 M K₂Cr₂O₇ solution is used for the titraction of 10 mL of Fe²⁺ solution in the acidic medium. The molarity of Fe²⁺ solution is ___________* 10^-2 M. (Nearest Integer)

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Meq of K₂Cr₂O₇ = Meq of Fe²⁺

(Molarity * Volume * nf) of K₂Cr₂O₇ = (molarity * volume * nf) of Fe²⁺

0.02 * 20 * 6 = M * 10 * 1

M = 0.24 M

Molarity = 24 * 10^-² M

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The total number of monobromo derivatives formed by the alkanes with molecular formula C₅H₁₂ is (excluding stereo isomers)___________.

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