CBSE > Class 12 > Chemistry | CBSE Board | Homework Help

In general, the molar conductivity of an electrolytic solution is the conductance of the volume of the solution containing a unit mole of electrolyte that is placed between two electrodes of unit area cross-section or at a distance of one-centimeter apart.

The unit of molar conductivity is S⋅m²⋅mol^-1.

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Surface chemistry mein kya Catalysis pura delete ho gya h..? And Ex se kn kn se ques delete hnge jara btana... Plz

Posted by Sonali Baral 4 years, 9 months ago

CBSE > Class 12 > Chemistry

3 answers

Jassi Midha 4 years, 9 months ago

Deleted question of chapter 5 are: 7, 13,16,17,18,19,20,21,22,24. Because emulsion and enzymes are also deleted from syllabus

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Drishty Kamboj 4 years, 9 months ago

Yeah whole of catalyst topic has been deleted and questions which are based on this topic too...

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Tanya ?? 4 years, 9 months ago

Hanji catalysis pura delete ho gya h pr mujhe exercise k questions ka nhi pta konse konse dlt honge...

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How much HCL in grams is required to prepare 250 mL of M/10 solution?

Posted by Aakriti Rustagi 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Drishty Kamboj 4 years, 9 months ago

Ac to ques M/10 means 0.1M sol now for 0.1moles per 1 l of sol,we have to calculate no. Of moles for 250 ml of sol ie 0.1/4 Let it be x(0.1/4 =x) This x is the no. Of moles of hcl in 250 ml of sol We have to calculate the mass of this x Mass of 1 mol of hcl =36.5 Mass of x=36.5*x

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Yogita Ingle 4 years, 9 months ago

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A solution containing 1.234g of calcium nitrate in 10 g of water boils at 100.995'c at 760mm. Calculate the vant hard factor for the salt at this concentration

Posted by Hritik Aryan 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Drishty Kamboj 4 years, 9 months ago

Vant hoff factor has been deleted this year....i guess

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Sonali Baral 4 years, 9 months ago

"i" is the van't hoff factor, then ΔTb=iKb×m (100.975−100)=i×0.52×164×101.23×1000 i=123×0.520.975×164=2.5 Now if x is the degree is dissociation, then Ca(NO3)2⇋ Ca2++ 2NO3− 1 0 0: Initially 1−x x 2x: At eqbm. ∴i=11−x+x+2x=11+2x=2.5⇒x=0.75 ∴ Percentage dissociation =75%

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Calculate equivalent mass of Na2CO3

Posted by Aakriti Rustagi 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

The reaction involved is,
Na₂CO₃ + HCl → NaCl + NaHCO₃
Equivalent mass of Na₂CO₃= 106/1 = 106.

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In ch 10 of organic its written that bond length of C-X increases as we move downward in. Group then according to this the boiling point should decrease as the size of X increase... But at other point its written that boiling point has the order RI>RBr>RCl>RF... CAN anyone justify this

Posted by Drishty Kamboj 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Drishty Kamboj 4 years, 9 months ago

Now can anyone answer why is Iodine a better leaving group if it has higher boiling point

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K S 4 years, 9 months ago

As the size and mass of halogen atom increases,there is an increase in the magnitude of van der waal's forces due to which the boiling point increases down the group.

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Under what conditions, Ecell =0 and ΔG = 0?

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Tanya ?? 4 years, 9 months ago

At equilibrium.

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Yogita Ingle 4 years, 9 months ago

At equilibrium

E_Cell=0

Therefore according to the formula, Δ_rG = −nFE_Cell
Δ_rG=0

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Write Nernst equation for the following reaction at 25°C. 2Al + 3Cu2+ 2Al3+(aq) + 3Cu

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

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A solution of solute X in benzene boils at 0.126°C higher than benzene. What is the molality of the solution? (Kb for benzene = 2.52 K/m) a. 0.05 b. 2 c. 1 d. 20

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

0 answers

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Which one of the following is the strongest base A. Sc(OH)3 B. La(OH)3 C. Lu(OH)3 D. Yb(OH)3

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

Which one of the following is the strongest base A. Sc(OH)3 B. La(OH)3 C. Lu(OH)3 D. Yb(OH)3

Ans : Sc(OH)₃

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A magnetic moment of 1.73 BM will be shown by which of the following: A. TiCl4 B. [CoCl6] 4- C. [Cu(NH3)4] 2+ D. [Ni(CN)4] 2

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

Electronic configuration of Cu²⁺ ion in [Cu(NH₃)₄]^2+.
Cu²⁺ ion =[Ar]³d⁹4s⁰.
∴Cu²⁺ion has one unpaired electron.
Magnetic moment of [Cu(NH₃)₄]²⁺(μ)=n(n+2)BM
where, n=no. of unpaired electrons
μ = √1(1+2) = √3 = 1.73BM
Whereas Ni²⁺ in [Ni(CN)₄]²⁻,Ti⁴⁺ in TiCl₄ and Co²⁺ ion [COCl₆]⁴⁻ has 2,0 and 3 unpaired electrons respectively.

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What is nuclide ?

Posted by Student Of The Year 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Gaurav Seth 4 years, 9 months ago

In nuclear physics and nuclear chemistry, the various species of atoms whose nuclei contain particular numbers of protons and neutrons are called nuclides. Nuclides are also characterized by its nuclear energy states (e.g. metastable nuclide ^242mAm). Each nuclide is denoted by chemical symbol of the element (this specifies Z) with the atomic mass number as superscript. Hydrogen (H), for example , consist of one electron and one proton. The number of neutrons in a nucleus is known as the neutron number and is given the symbol N. The total number of nucleons, that is, protons and neutrons in a nucleus, is equal to Z + N = A, where A is called the atomic mass number.

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Arrange propanone, ethanol, dimethyl ether and propanal in increasing order of their boiling points.

Posted by Dileep Meena 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Sneha Panwar 4 years, 9 months ago

Remember a simple step that as the branching increases boiling point decreases. ethanol >propanal >propanone >dimethy ether

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Zr and Hf have almost equal atomic and ionic radii because of A. Diagonal relationship B. Of lanthanoid contraction C. Of actinide contraction D. Both belong to f block of elements.

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Gaurav Seth 4 years, 9 months ago

ANSWER: B. Of lanthanoid contraction
This is because of poor screening effect by 4f electrons,which lead to the lanthanoid contraction.Hence,is the reason of Zn and Hf have almost equal atomic size.

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The conversion of a carboxylic acid to α-bromocarboxylic acid using red phosphorus and bromine is A. Cannizzaro’s reaction B. Hell Vohlard Zelinsky reaction C. Aldol condensation D. Kolbe’s reaction.

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Gaurav Seth 4 years, 9 months ago

B. Hell Vohlard Zelinsky reaction

Hell Volhard Zelinsky (HVZ) reaction:
This reaction involves alpha bromination of carboxylic acids. Carboxylic acids react with chlorine or bromine in presence of small amount of red phosphorous to give alpha halo carboxylic acids.

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Which of the following is a tertiary amine? A.1-methylcyclohexylamine. B. triethylamine C.tert- butylamine D. N- methylaniline.

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

Triethyl amine (C₂H₅)₃N is tertiary amine

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Which of the following is a purine base: A. Guanine B. Cytosin C. Thymine D. Uracil

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Promita Das 4 years, 9 months ago

Guanine

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Yogita Ingle 4 years, 9 months ago

Purines are compounds that contain a six- membered ring that has nitrogen in it as well. This ring is further fused with an imidazole ring. Thus, purines are structures that have two rings. Purines that are found in the nucleic acids are Adenine (A) and Guanine (G).

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Which of the following defects decreases density? A.Interstitial defect. B. Schottky defect C. Frankel defect D. none of the above.

Posted by Vicky Wani 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Yogita Ingle 4 years, 9 months ago

Vacancy and Schottky defect which lead to decrease the density both are the types of a stoichiometric defect. In case of Frenkel defect and interstitial defect, there is no change in density of substance.

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Gaurav Seth 4 years, 9 months ago

ANSWER : B. Schottky defect

Vacancy and Schottky defect which lead to decrease the density both are the types of a stoichiometric defect. In case of Frenkel defect and interstitial defect, there is no change in density of substance.

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Excess of Lithium make the LiCl pink . Explain

Posted by Neeraj Kaushik 4 years, 9 months ago

CBSE > Class 12 > Chemistry

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Give the one uses of CHI3

Posted by Neeraj Kaushik 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

Uses of iodoform (CHI₃)

Iodoform was used earlier as an antiseptic, but now it has been replaced by other formulations-containing iodine-due to its objectionable smell. The antiseptic property of iodoform is only due to the liberation of free iodine when it comes in contact with the skin.

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How write in lab manual on which topic?

Posted by Vishwa Rajput 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Sneha Singh 4 years, 9 months ago

First write experiment then observation and last inference

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HCL was passed through the solution of CaCl2, Mgcl2 and Nacl. Which compond(s) crystallise(s)

Posted by Rachana Bhajantri 4 years, 9 months ago

CBSE > Class 12 > Chemistry

0 answers

ANSWER

To study the presence of oxalate ion content in guava fruits at different stage of ripining... Project

Posted by Sk Azad Sk Azad 4 years, 9 months ago

CBSE > Class 12 > Chemistry

0 answers

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Conclusion of paper chromatography

Posted by Pratiksha Gangane 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Gaurav Seth 4 years, 9 months ago

1) Paper Chromatography:

It is the simplest type of chromatography. In this method, a special type of paper called chromatographic paper or ordinary filter paper is used.

A line is drawn near the bottom edge of the paper. The paper is dipped in a solvent and taken in a beaker so that the line drawn on the paper is above the level of the solvent.

Stationary phase: Filter paper

Mobile phase: Solvent

As the solvent rises on the paper, it takes along with it the drop of the substances.

The component of the drop which is more soluble rises faster and we see various spots on the paper, each indicating a component of the mixture.

The paper is then removed from the solvent and dried.

(2) Crystallisation:

This method is based on the differences in the solubility of solids in a liquid.

The process of formation of crystals from a hot saturated solution caused by cooling is called crystallisation. It is a process in which a solution containing more of the solid component is slowly evaporated.

Pure sugar is obtained from its solution in water by the process of crystallisation.

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Cbsc board chemistry practical

Posted by Mohd Abubakr 4 years, 9 months ago

CBSE > Class 12 > Chemistry

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What is the difference between rhombic sulphur and monoclinic sulphur..?

Posted by Nidhi Kalmodiya 4 years, 9 months ago

CBSE > Class 12 > Chemistry

2 answers

Yogita Ingle 4 years, 9 months ago

Rhombic sulphur (α-sulphur)

Rhombic sulphur is crystalline in nature and has octahedral shape. On heating the solution of roll sulphur in CS2 we get rhombic sulphur. It is yellow with a melting point of 385.8K and specific gravity 2.06. Rhombic sulphur cannot be dissolved in water but can be dissolved in benzene, ether, alcohol etc.

Monoclinic sulphur (β-sulphur)

When we take a dish and melt rhombic sulphur in that dish we obtain monoclinic sulphur after cooling it. In this process we make two holes in the crust and pour out the remaining liquid. After this we get colourless needle-shaped crystals of β-sulphur when the crust is removed.

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Gaurav Seth 4 years, 9 months ago

Rhombic sulfur (α-sulfur)	Monoclinic sulfur (β- sulfur)
1. It is a pale yellow coloured solid.	1. It is bright yellow solid
2. It forms orthorhombic crystals	2. It forms needle-shaped monoclinic crystals
3. Its melting point is 385.8 K.	3. Its melting point is 393 K.
4. Its density is 2.06 g/cm³	4. Its density is 1.98 g/cm³
5. It is insoluble in water and soluble in CS₂	5. Soluble in CS₂
6. It is stable below 369 K and transforms to β-sulfur above this temperature	6. It is stable above 369 K and transforms into α-sulfur below this temperature.
7. It is prepared by the evaporation of rolls sulfur in CS₂.	7. It is prepared from rhombic sulfur.

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An alpha-helix is a structural feature of what?

Posted by यShi Awaस्थी 4 years, 9 months ago

CBSE > Class 12 > Chemistry

1 answers

Yogita Ingle 4 years, 9 months ago

The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O. group of the amino acid located three or four residues earlier along the protein sequence.

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Any body have oswaal sample paper for class-12 for 2021 exam?

Posted by Aditya Kumar 4 years, 9 months ago

CBSE > Class 12 > Chemistry