Ask questions which are clear, concise and easy to understand.

How can you explain higher stability of BCl3 as compared to TlCl3

Posted by Shadab Mahmood (Jan 17, 2017) (Question ID: 1423)

  • Answers:
  • Both boron and thallium belong to group 13 of the periodic table. Boron does not show inert pair effect as it does not have d or f electrons. As we go down the group, the shielding effect of the electrons also decrease therefore the increased nuclear charge down the group is not neutralized by the poor shielding effect of the electrons in the inner orbitals.Due to this the inert pair effect becomes more and more predominant and the s electrons of the valency shell experiences strong attraction .This effect is maximum in thallium and therefore only the 6p1 electrons take part in the bond formation. This makes +1 oxidation state most stable in case of thallium. Therefore TlCl is stable and TlCl3 is unstable. In case of BCl3 , boron does not have d or f orbital , so all the valence electron in the 2s and 2p orbital takes part in the bond formation making BCl3 stable.

    Answered by Naveen Sharma (Jan 17, 2017)
    Thanks (1)
  • Add Answer

What is the active mass of water

 

Posted by Sajal Jain (Jan 15, 2017) (Question ID: 1376)

  • Answers:
  • Active mass is defined as the molar concentration ie. number of Gram-moles per litre

    Active mass for pure liquids and solids is Always taken 1.

    if not pure water then
    For water, 
    density = 1 g/mL = 1000 g/L 
    Molar mass = 18.015 g/mol 

    so 

    1000 g/L = (1000 g/L)/(18.015 g/mol) = 55.51 mol/L

    Answered by Naveen Sharma (Jan 15, 2017)
    Thanks (2)
  • Add Answer

Nacl is soluble in water and insoluble in petrol why?

 

Posted by Udit Vaibhav (Jan 13, 2017) (Question ID: 1350)

  • Answers:
  • Just remember that like dissolves like. The same way, polar dissolves polar compounds. In this case, NaCl is polar so it gets dissolved in water(which we know is also polar). On the other hand, petroleum is a non polar compound, Therefore, NaCl does not dissolve in it. 

    Answered by yakshith k (Jan 15, 2017)
    Thanks (0)
  • Sodium chloride is an ionic molecule. There exists electronegativity difference between Sodium and Chlorine, which gives polarity to the molecule. Thus sodium chloride is polar molecule.


    Generally polar molecules will soluble in polar solvents and insoluble in non-polar solvents. Non-polar molecules will soluble in non-polar solvents and insoluble in polar solvents.


    As sodium chloride is polar molecule it will be soluble in polar solvents like water. And insoluble in petrol (as it is non-polar solvent).

    Answered by Naveen Sharma (Jan 13, 2017)
    Thanks (0)
  • Add Answer

Why lithium halides are somewhat covalent?

Posted by Bikash Adhikari (Jan 13, 2017) (Question ID: 1336)

  • Answers:
  • We know that, electronegative nature decreases down the group, so Li will have higher electronegative character than other elements of the group, and also it has very small size the lithium halides become covalent in nature.

    It is because, the small size of Li+ cation will have the maximum tendency to withdraw electrons from anions and so it polarizes the bond and in this process, it distorts the electron clouds of anions which neutralizes some of the charge, and their increases a covalent character.

    The Fajan's rule explains that smaller the size of atom higher will be polarizing capacity and so the covalent character will be larger.

    So the Lithium halides become partially covalent in nature.

    Answered by Naveen Sharma (Jan 13, 2017)
    Thanks (1)
  • Add Answer

What ie photoelectric effect

Posted by Rajnish Singh (Jan 12, 2017) (Question ID: 1305)

  • Answers:
  • Under the right circumstances light can be used to push electrons, freeing them from the surface of a solid. This process is called the photoelectric effect (or photoelectric emission or photoemission), a material that can exhibit this phenomena is said to be photoemissive, and the ejected electrons are called photoelectrons; but there is nothing that would distinguish them from other electrons. All electrons are identical to one another in mass, charge, spin, and magnetic moment.

    Answered by Payal Singh (Jan 12, 2017)
    Thanks (0)
  • The photoelectric effect or photoemission is the production of electrons or other free carriers when light is shone onto a material. Electrons emitted in this manner can be called photoelectrons.

    Answered by Naveen Sharma (Jan 12, 2017)
    Thanks (0)
  • Add Answer

Why is Ga smaller in size than Al? 

Posted by Hitesh Saini (Jan 07, 2017) (Question ID: 1130)

  • Answers:
  • The size of Ga is sampler than Al due to poor screening effect .The electrons in 3d of Ga are occupied ,they have poor screening effect and hence less influence to decrease effective nuclear charge .Therefore electrons in Ga experience more force of attraction than Al resulting in decrease in size.

    Answered by shruti dadhwal (Jan 07, 2017)
    Thanks (0)
  • Add Answer

how hydrogen is different from halogens?

 

Posted by Muskan Goyal (Jan 04, 2017) (Question ID: 1063)

  • Answers:
  • Hydrogen is the lightest element having atomic mass 1 while halogens are group of elements that includes F, Cl, Br, I etc. Hydrogen acts as both electropositive and electronegative element but halogens are hightly electronegative in nature.

    Answered by RAJENDRA SINGH (Jan 04, 2017)
    Thanks (1)
  • Add Answer

Why does the colour of NaCl chage into blue whe we add some lemon juice? 

 

Posted by Kirtti RANJAN MISHRA (Jan 03, 2017) (Question ID: 1054)

Why the salts of superoxides are coloured?

Posted by Bibhu Mukhopadhyay (Jan 01, 2017) (Question ID: 979)

  • Answers:
  • They are coloured because of paramagnetic nature of the compound O2-.

    According to molecular orbital theory it has an unpaired electron hence it is paramagnetism.

    Answered by Devanshu Agarwal (Jan 01, 2017)
    Thanks (1)
  • Add Answer

Why diffusion is not in the case of earth with respect to space whether  earth has many gases? 

Posted by arnav negi (Jan 01, 2017) (Question ID: 977)

What is polarity

 

Posted by piyush jain (Dec 28, 2016) (Question ID: 915)

  • Answers:
  • Polarity is separation of electric charge leading to a molecule having electric dipoles.polar molecule interact through intermolecular forces.for example H2O is a polar molecule but CO2 is non polar molecule in which dipoles cancel each other.

    Answered by shruti dadhwal (Jan 07, 2017)
    Thanks (0)
  • Polarity is a physical property of compounds which relate to other physical properties, such as melting and boiling points or solubility. Bond polarities arise from bonds between atoms of different electronegativity. A molecule can be ionic, polar or non-polar.

    A polar molecule is formed when one end of a molecule has a positive charge and the opposite end has a negative charge, thus creating electrical poles. A non-polar molecule does not have charges at the ends as the electrons are distributed more symmetrically and cancel each other out.

    When trying to create a solution, a polar molecule does not mix with a non-polar molecule. An example of this is seen with water, a polar molecule and oil, anon-polar molecule; the two molecules cannot mix to form a solution. However, water and alcohol can mix to form a solution as they are both polar molecules.

    Answered by Naveen Sharma (Dec 29, 2016)
    Thanks (0)
  • Add Answer

The equilibirum constant kfor the reaction H2+I2= HI

is 130 at 510k.calculate kc for the reaction

Posted by Ramesh makadiya (Dec 26, 2016) (Question ID: 853)

  • Answers:
  • Given

    Kp=130.

    T=510K

    We know that,  Kp=Kc(RT)n 

    balance equation    H2+I22HI    

    Therfore,

    Kc=Kp/(RT)n

    =130(8.314*510)0

    Kc=130

    Answered by yakshith k (Dec 27, 2016)
    Thanks (0)
  • Add Answer

What do you mean by hydride gap?

Posted by Athira Shaji (Dec 23, 2016) (Question ID: 808)

  • Answers:
  • The metals of 7th, 8th and 9th groups in the periodic table do not form hydrides and this region of periodic table is referred to as the hydride gap.

    Answered by Naveen Sharma (Dec 23, 2016)
    Thanks (0)
  • The metals of group 7,8,9 of the periodic table do not form hydrides as they have low affinity to combine with hydrogen in their normal state.This region is called hydride gap.

    Answered by shruti dadhwal (Dec 23, 2016)
    Thanks (0)
  • Add Answer

An open vessel contains 200 mg of air at 17 Celsius  wht weight percentage of air would be expelled if vessel is geared to 117 Celsius 

Posted by Meghna Rajeev (Dec 14, 2016) (Question ID: 754)

  • Answers:
  • Suppose volume of 200 mg of air at 170C = V ml
    As pressure remains constant. Because vessel is open & only atm. pressure is acting.
     V2 = 1.34 V 
    Volume of air expelled = 1.34 V - V = 0.34 V 
       Mass of 1.34 V air at 1170C = 200mg 
       Mass of 0.34 V air at 1170C =  x 0.34 mg 
    Mass % of air expelled =  x 100 = 25.37 %

    Answered by Naveen Sharma (Dec 14, 2016)
    Thanks (0)
  • Add Answer

Calculate pH for 0.001M NaOH

Posted by Medha Krishna (Dec 14, 2016) (Question ID: 752)

  • Answers:
  • NaOH is a strong base that dissociates completely 
    Therefore [OH-] = [NaOH] = 0.001M 

    First calculate the pOH of the solution : 
    pOH = -log [OH-] 
    pOH = -log 0.001 
    pOH = 3.00 

    pH = 14.00 - pOH 
    pH = 14.00 - 3.00 
    pH = 11.00

    Answered by Naveen Sharma (Dec 14, 2016)
    Thanks (0)
  • Add Answer

how to give iupac name to organic compounds

Posted by Navpreet Kaur (Dec 09, 2016) (Question ID: 718)

  • Answers:
  • IUPAC naming involves certain set of rules.The first step is to identify the longest carbon chain and name it as alkane,alkene or alkyne depending upon the bond if it is single, double or triple bond. The alkane chain when used as substituent is named as alkyl group. 

    Name the carbon chain such that the substituents get the least position.The type of group attached to the carbon chain will decide the suffix attached to the IUPAC name.A cyclic compound is designated by prefix cyclo group attached to it. 

    Answered by shruti dadhwal (Dec 10, 2016)
    Thanks (0)
  • Add Answer

harmful effects of cold drinks?

 

Posted by harsh vardhan (Dec 02, 2016) (Question ID: 672)

  • Answers:
  • Artificial Sweeteners– In diet sodas, aspartame is used as a substitute for sugar, and can actually be more harmful. It has been linked to almost a hundred different health problems including seizures, multiple sclerosis, brain tumors, diabetes, and emotional disorders. It converts to methanol at warm temperatures and methanol breaks down to formaldehyde and formic acid. Diet sodas also increase the risk of metabolic syndrome, which causes belly fat, high blood sugar and raised cholesterol.

    Phosphoric Acid -Soda contains phosphoric acid, which interferes with the body’s ability to absorb calcium and can lead to osteoporosis, cavities and bone softening. Phosphoric Acid also interacts with stomach acid, slowing digestion and blocking nutrient absorption. 

    The Sugar! – A single can of soda contains the equivalent of 10 teaspoons of sugar. This amount of sugar, especially in liquid form, <a href="http://wellnessmama.com/podcast/stop-sugar-madness/">skyrockets the blood sugar and causes an insulin reaction in the body</a>. Over time, this can lead to diabetes or insulin resistance, not to mention weight gain and other health problems. Soft drink companies are the largest user of sugar in the country.

     

    Caffeine– Most sodas contain caffeine, which has been linked to certain cancers, breast lumps, irregular heart beat, high blood pressure, and other problems.

    The Water– The water used in soda is just simple tap water and can contain chemicals like chlorine, fluoride and traces of heavy metals.

    Obesity– Harvard researchers have recently positively linked soft drinks to obesity. The study found that 12 year olds who drank soda were more likely to be obese than those who didn’t, and for each serving of soda consumed daily, the risk of obesity increased 1.6 times.

    Extra Fructose– Sodas contain High Fructose Corn Syrup, which obviously comes from corn. Most of this corn has been genetically modified, and there are no long term studies showing the safety of genetically modified crops, as genetic modification of crops has only been around since the 1990s. Also, the process of making High Fructose Corn Syrup involves traces of mercury, which causes a variety of long term health problems.

    Lack of Nutrients– There is absolutely no nutritional value in soda whatsoever. Not only are there many harmful effects of soda, but there are not even any positive benefits to outweigh them.  Soda is an unnatural substance that harms the body.

    Dehydration– Because of the high sugar, sodium and caffeine content in soda, it dehydrates the body and over a long period of time can cause chronic dehydration.

    Bad for the teeth– Drinking soda regularly causes plaque to build up on the teeth and can lead to cavities and gum disease.

     

    Answered by Naveen Sharma (Dec 03, 2016)
    Thanks (0)
  • Add Answer

how to introduce a triple bond b/w two carbon atoms

Posted by ankit yadav (Nov 22, 2016) (Question ID: 617)

  • Answers:
  • 1. Dehydrohalogenation of vicinal or geminal dihalides: A vicinal di halide such as 1,2 dichloroethane when treated with sodamide(NaNH2) yields Ethyne. 

    2.Dehalogenations of tetrahaloalkanes.

    3.From Calcium Carbide:Higher homologues can be prepared by nucleophilic displacement by acetylide anion. Secondary halodes gives poor yield while tertiary halides cannot be used.

    4.By heating Iodoform with silver:

    2CHI3+6AgheatC2H2+6Ag

       

      

    Answered by yakshith k (Dec 16, 2016)
    Thanks (0)
  • You can get your doubts cleared instantly, 24/7 with IIT/AIIMS tutors on HashLearn. Download here: http://bit.ly/2fDYZtb

    Answered by Ashwin S (Nov 28, 2016)
    Thanks (0)
  • Add Answer

Syn gas is major source for the production of dihydrogen. Earlier it was obtained only by coal

gasification. But scientists of many developed countries now a days obtained it from biomass

gasification.

(i) Write the main difference between coal gasification and biomass gasification.

(ii) Why is biomass gasification is more advantageous over coal gasification for the generation

of syn gas?

(iii) Write the balanced reaction showing production of dihydrogen from syn gas.

(iv) What values are associated with the scientists of developed countries.

Posted by Trisha Mandal (Nov 18, 2016) (Question ID: 579)

  • Answers:
  • (i) Biomass gasification is a process of converting solid biomass fuel into a gaseous combustible gas (called producer gas) through a sequence of thermo-chemical reactions. 

    Coal gasification is the process of producing syngas–a mixture consisting primarily of methane (CH4), carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2) and water vapor (H2O)–fromcoal and water, air and/or oxygen.

    (ii) Biomass gasification is more advantageous over coal gasification because firstly, coal is fossil fuel and extraction of coal is a cumbersome process with risks of fire accidents during excavation. While, biomass gasification is a simple way of energy tranformation. Biomass is easily available and efficiency in the process is also high comparitively.

    (iii) C(s)+H2O(g)473-1273KCO(g)+H2(g)

     

    Answered by yakshith k (Dec 19, 2016)
    Thanks (1)
  • Add Answer

Give two reactions to show acidic character of alkynes?

Posted by Trisha Mandal (Nov 18, 2016) (Question ID: 578)

  • Answers:
  • 1.Formation of sodium acetylides.

    C2H2NaHCCNaNaNaCCNa

    2.Formation of copper acetylide.

    C2H2+2AgNO3+NH4OHAgCCAg+2NH4NO3+2H20

    Answered by yakshith k (Dec 16, 2016)
    Thanks (1)
  • Add Answer

Which d-orbital does not have four lobes and what is its shape called?

Posted by Trisha Mandal (Nov 18, 2016) (Question ID: 577)

  • Answers:
  • The d orbital which does not have four lines is called dz2 and is shape is called clover leaf shape.All other d orbital d xy,d yz,d zx and d x2-y2 have four lobes and are called to have double dumb bell structure.

    Answered by shruti dadhwal (Dec 06, 2016)
    Thanks (1)
  • Add Answer

which isotope of hydrgen is radioactive

Posted by Om Deshmukh (Nov 17, 2016) (Question ID: 573)

  • Answers:
  • There are three isotopes of protium, deuterium and tritium .out of the three isotopes, tritium is the isotope which is radioactive in nature and it is used in spectroscopy.

    Answered by shruti dadhwal (Dec 06, 2016)
    Thanks (0)
  • Deuterium is a hydrogen isotope consisting of one proton, one neutron and one electron. It has major applications in nuclear magnetic resonance studies. Tritium is a hydrogen isotope consisting of one proton, two neutrons and one electron. It is radioactive, with a half-life of 12.32 years.

    Answered by AKSHAY KUMAR (Nov 18, 2016)
    Thanks (0)
  • Add Answer

"BeH2 molecules has zero diopole moment althrough the Be-H bonds are polar" Explain

Posted by Neha Kumari (Nov 17, 2016) (Question ID: 572)

  • Answers:
  • The Be-H bonds are polar due to electronegativity difference in them but the molecule BeH2 is non polar because the structure of BeH2 is linear where both Be-H bonds are opposite to each other and cancels each others polarity making it a non polar molecules with dipole moment zero

    H<---Be-->H

    Answered by shruti dadhwal (Dec 06, 2016)
    Thanks (0)
  • The dipole moment of BeHhas 0 because the two equal bond dipole are present in opposite directions and cancel the effect of each other.

    HBeH

    Answered by Trisha Mandal (Nov 18, 2016)
    Thanks (1)
  • Add Answer

what is the canonical structure for NO3+

Posted by meera nair (Nov 13, 2016) (Question ID: 546)

  • Answers:
  • Answered by yakshith k (Dec 16, 2016)
    Thanks (0)
  • Add Answer

If water is assumed to be perfect gas,molar enthalpy change for vapourisation of 1 mole of H2O at 1 bar and 100 degree celcius is 41 KJ per mole,calculate internal energy change when 1 mole of H2O is converted into ice

Posted by Harsh sinha (Nov 10, 2016) (Question ID: 508)

how to draw lewis dot structure of NO2?

Posted by Radha Jittu (Nov 06, 2016) (Question ID: 494)

  • Answers:
  • We take the number if valence electrons in each of the atom and draws it to complete the octet.the nitrogen carries one negative charge making it having 5+1=6 Valene electrons .thus the structure becomes

    O = N - O

    Answered by shruti dadhwal (Dec 06, 2016)
    Thanks (0)
  • O-N=O

    Answered by Trisha Mandal (Nov 18, 2016)
    Thanks (0)
  • Add Answer

A chemical reaction is carried out by starting with 1 mol each of H2 and I2 in closed vessel at 717K . No more change in concentration is observed after 1.56 mol of HI is formed. If we start the reaction with 2 mol os HI under similar conditions,how many moles of H2 and Iwill be formed?

Posted by Rashmi Singh (Nov 02, 2016) (Question ID: 477)

what is balancing?

Posted by Anil Vishwakarma (Nov 01, 2016) (Question ID: 470)

  • Answers:
  • Balancing of reaction means making the number of atoms equal on both sides of the reaction( reactants and products) .We move step by step to write a balanced equation making number of atoms equal on both sides.

    Answered by shruti dadhwal (Dec 06, 2016)
    Thanks (0)
  • Add Answer

Whose bond angle ( F-C-F ) is greater - CH2For CHF3 ??? Explain with reason. 

Posted by Aman Pandey (Oct 16, 2016) (Question ID: 407)

  • Answers:
  • The C-H and C-F bonds are polar and so the electron density will be shifted towards carbon in the C-H bonds and towards fluorine in the C-F bonds. Directing orbitals with more s character towards the hydrogens is stabilizing, while directing orbitals of less s character towards the fluorine is destabilizing but to a lesser extent.

    Answered by yakshith k (Dec 19, 2016)
    Thanks (0)
  • Add Answer

what do you mean by ionisation enthailpy and atomic radiii/????????

 

 

Posted by shivam kumar (Oct 12, 2016) (Question ID: 371)

  • Answers:
  • The amount of energy required to remove one electron from outermost shell of an atom is called ionisation enthailapy. The distance between the nulceus the outermost shell is called atomic radius.

    Answered by RAJENDRA SINGH (Oct 12, 2016)
    Thanks (0)
  • Add Answer

Sponsored Links

Download Mobile App

banner

Subscribe by E-mail

For Latest News and Updates from myCBSEguide.com
Enter your email address:

Connect via Facebook

Sponsored Links