Class 12th

For the first order reaction A → 2B, 1 mole of reactant A gives 0.2 moles of B after 100 minutes. The half life of the reaction is _____ min. (Round off to the Nearest Integer).
[Use : ln2 = 0.69, ln 10 = 2.3 Properties of logarithms : ln x? = y ln x; ln(x/y) = lnx – lny ]

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A → 2B
t = 0: 1 mole 0
after 100 min: (1 - 0.1) mol 0.2 mol
K = (1/t)ln [a/ (a-n)]
K = (2.303/100)log (1/0.9) min? ¹
0.693/t? /? = (2.303/100) [log10 - log9] = (2.303/100) x 0.046
t? /? = 69.3 / (2.303 x 0.046) = 654.15 min
Ans. = 654 (the nearest integer)

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Class 12th Solutions

In a solvent 50% of an acid HA dimerizes and the rest dissociates. The van't Hoff factor of the acid is _____ *10⁻². (Round off to the Nearest Integer).

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i = total no. of particles after dissociation/association / total no. of particle before dissociation/association
HA? H? + A? (Dissociation)
0.5a
2HA → (HA)? (Association)
0.5a/2
i = (a + 0.25a)/a = 125 x 10? ²
Ans. = 125

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Percentage packing fraction of diamond is x (approximately), and the number of particle per unit cell is y. Then the value of x + y is

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Class 12th Coordination Compounds

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Percentage packing fraction of diamond is 34% and number of particle per unit cell is 8.

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Out of following the number of complexes which are diamagnetic is / are
(i) [Co(H₂O)₆]Cl₃
(ii) [Co(NH₃)₆]Cl₂
(iii) [Fe(CO)₅]
(iv) [Ni(NH₃)₆]²⁺
(v) K₂[NiF₆]
(vi) K₂[PtCl₄]
(vii) Na₂[ZnCl₄]

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[Co (NH? )? ]Cl? and [Ni (NH? )? ]²? are paramagnetic.

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If X metal atoms occupying the corners, Y atom at cube centre and Z atoms at the centres of the edges, then if the co-ordination number of X w.r.t. Z is a and that of Y w.r.t. Z is b, then the value a + b is

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Coordination no.

X 6
Y 12

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Consider the above reaction, and choose the correct statement:

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Class 12th Environmental chemistry

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Trans product is more stable than Cis. ( Trans product feel less repulsion due to opposite direction)

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Biochemical Oxygen Demand (BOD) is the amount of oxygen required (in ppm)

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BOD is the amount of oxygen required by bacteria to break down the organic matter present in a certain volume of sample of water.

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Which polymer has 'chiral' monomer(s)?

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Polymer Monomers
Buna-N CH? = CH – CH = CH?
and
CH? = CH – CN
Neoprene H? C = C (Cl) – CH = CH?
Nylon-6, 6 Hexamethylenediamine + Adipic Acid
PHBV CH? – CH (OH) – CH – COOH
and
CH? – CH? – CH (OH) – CH? – COOH

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Out of following in which retention of configuration in product P will take place?

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Inversion + Inversion = Retention

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To an aqueous solution containing ions such as Al³⁺, Zn²⁺, Ca²⁺, Fe³⁺, Ni²⁺, Ba²⁺ and Cu²⁺ was added conc. HCl, followed by H₂S.
The total number of cations precipitated during this reaction is / are:

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