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Why ionization energy is less for oxygen than nitrogen?

Posted by Krithik Krithik (Jul 28, 2017 5:30 a.m.) (Question ID: 6984)

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  • This is due to an electron being added to an already half full orbital in oxygen, which results in electron electron repulsion, which will lower the ionisation energy. Nitrogen also has the added stability of a half filled shell of electrons in the 2p shell.

    Answered by Payal Singh (Jul 28, 2017 8:13 a.m.)
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What is charge to radius ratio? 

Does the first member of 13th group of p- block element has small charge to radius ratio??

 

Posted by Tanisha Garg (Jul 27, 2017 10:38 p.m.) (Question ID: 6983)

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  • Charge -Radius Ratio: It is a measuring technique which describes the metallic character of elements.

    According to charge/radius ratio, the element having c/r less than 7.0 are called as metallic, ane those elements which have charge /radius ratio greater than 7.0 are called as non-metallic, whereas it has been seen that the element which has charge/radius ratio slightly greater than 7.0 are called as semi-metals or more commonly called as semi -conductor.

    Answered by Payal Singh (Jul 28, 2017 8:14 a.m.)
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Why do you think there is no example of a gas - gas colloid?

 

Posted by Arpit Gainan (Jul 27, 2017 10:04 p.m.) (Question ID: 6982)

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  • All gases are inherently miscible (completely soluble in each other), so by definition there is no such thing as a gas-gas colloid.

    Answered by Payal Singh (Jul 28, 2017 8:15 a.m.)
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Why the reaction of ester is intially slow and fast after sometime?

 

Posted by Chetan Joshi (Jul 27, 2017 9:52 p.m.) (Question ID: 6981)

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  • Ester hydrolysis can be represented as: Ester + Water → Acid + Alcohol

    The acid produced in the reaction acts as a catalyst and makes the reaction faster. Substances that act as catalysts in the same reaction in which they are obtained as products are known as autocatalysts.

    Answered by Payal Singh (Jul 28, 2017 8:15 a.m.)
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What is hypertension and hypotension?

Posted by Saket19 Shukla (Jul 27, 2017 8:24 p.m.) (Question ID: 6980)

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  • Hypertension is a medical term for what we commonly call as high blood pressure. It is a health condition, but not exactly a disease, in which the blood pressure rises above the normal range. This is just the opposite of Hypotension or low blood pressure in which the blood pressure falls below the normal range.

    Answered by Payal Singh (Jul 28, 2017 8:16 a.m.)
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differentiate between impact and non-impact printers giving two points each

 

Posted by Naboneeta Mandal (Jul 27, 2017 7:57 p.m.) (Question ID: 6979)

  • IMPACT PRINTERS

    1. Impact printers operate by having an element strike the paper.

    2. They are extremely slow, with printing just 10 characters per second.

     

    NON-IMPACT PRINTERS

    1. The printheads of non-impact printers do not strike the page.

    2. They are somehow, faster than Impact Printers.

    Posted by Chander Singh (Jul 28, 2017 5:54 a.m.)
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Evaluate :- 1+i2+i4+i6+.................+i2n

Posted by Shriom Yadav (Jul 27, 2017 7:48 p.m.) (Question ID: 6978)

  • Here i is stands for  iota

    Posted by Shriom Yadav (Jul 27, 2017 8:04 p.m.)
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If the units of length mass and force are taken as fundamental units then find the dimension of time?

Posted by Tarun Rastogi (Jul 27, 2017 7:28 p.m.) (Question ID: 6977)

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Why is electron gain enthalpy of flourine is less negative than that of chlorine?

Posted by Sreenivas V (Jul 27, 2017 6:36 p.m.) (Question ID: 6976)

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  • Electron gain enthalpy is defined as the enthalpy change associated with an isolated gaseous atom  when it gains an electron to form its corresponding anion.

    X(g)  +    e- --------->   X- (g)   

    General trend for variation of electron gain enthalpy  down the group.

    On moving down the group the atomic size as well as nuclear charge increases. But the effect of increase in atomic size is much more pronounced than that of nuclear charge. Thus , the additional electron feels less attraction  with the result electron gain enthalpy becomes less  negative on going down the group.

    However in case of halogens , there happens to be an exception  as  given below.

    F =  -328 kj /mol

    Cl  =  -349 kj /mol

    Br  = -325  kj /mol

      I  =  -295 kj / mol 

    Electron gain enthalpy  of  F  is less negative than Cl because of its smaller size. The additional electron in case of F will be added to 2p orbital , while in case of Cl it will go in the 3p orbital. as 2p orbital occupies a smaller region of space than that of 3p orbital, it will be more compact  , due to which electron - electron repulsion would be more. Therefore, the incoming electron would be accepted  with much less ease in case of  F.  Hence , its electron gain enthalpy is less negative than Cl.

    Answered by Dr. Kamlapati Bhatt (Jul 27, 2017 7:51 p.m.)
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how to get full marks in biology especially in the chapter herdiatary and evolution should we study that all practically

Posted by Vighnesh 007 (Jul 27, 2017 6:20 p.m.) (Question ID: 6975)

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how we get the lens equation (prrof)

Posted by Vighnesh 007 (Jul 27, 2017 6:19 p.m.) (Question ID: 6974)

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Prove that (5-2√3)2 is irrational number?

Posted by Rahul Dagar (Jul 27, 2017 3:18 p.m.) (Question ID: 6973)

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  • We will prove it in a  same way as we prove that {tex} \sqrt{3}{/tex} is an irrational number..

    Let us assume that {tex}({5-2\sqrt{3}})^2{/tex} is a rational number. 

    Then          {tex}( {5-2\sqrt{3}})^2={p\over q}{/tex}    where p and q are co-prime.

    {tex} =>{/tex}  {tex}25-2×5×2{\sqrt 3}+(2{\sqrt 3})^2={p\over q}{/tex}    [by using {tex}(a-b)^2=a^2-2ab+b^2{/tex}

                                 {tex}25-20{\sqrt 3} +4×3={p\over q}{/tex}

                                   {tex}25-20{\sqrt 3}+12={p\over q}{/tex}

                                             {tex}37-20{\sqrt 3}={p\over q}{/tex}

                                            {tex}37+{p\over q}=20{\sqrt3 }{/tex}

                                           {tex}{37\over 20} +{p\over 20q}={\sqrt 3}{/tex}

          Clearly L.H.S. is a sum of two rational number and therefore L.H.S  is rational.

    So {tex}{\sqrt 3}{/tex} is a rational number.

    But  we know that {tex}{\sqrt3}{/tex} is an irrational number.So our assumption is wrong.

    Hence {tex}({5-2\sqrt{3}})^2{/tex}is an irrational number.

    Answered by Dharmendra Kumar (Jul 27, 2017 6:27 p.m.)
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  • prove (5-2 root3)2 = 25-20root 3+12=p/q consider it as rational first

    but solving it we get that root 3 could be represented as rational but it is irrational number thus our assumption that (5-2 root 3)2was wrong and hence it is irrational

    Answered by Vighnesh 007 (Jul 27, 2017 6:14 p.m.)
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Q.  Difference between x-t curve and v-t curve? 

Q. Can x-t curve give acceleration graph? 

Posted by Kaushik Mehta (Jul 27, 2017 3:09 p.m.) (Question ID: 6972)

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Features of alluvial soil 

Posted by Rajesh S (Jul 27, 2017 12:42 p.m.) (Question ID: 6971)

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  • alluvial soil - a fine-grained fertile soil deposited by water flowing over flood plains or in river beds. alluvial deposit, alluvial sediment, alluvium, alluvion - clay or silt or gravel carried by rushing streams and deposited where the stream slows down. Alluvial soil as a whole is very fertile. These soils contain adequate proportion of Potash, Lime and Phosphoric acid. Silk, clay, gravel and sand the main constituents of alluvial soil. It is commonly found in riverbed and flood plains.

    Answered by Dr Pathikrt Banerjee (Jul 27, 2017 5:44 p.m.)
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Why electric flux of cylindrical vessel is zero at the end? 

Posted by Shubhi Shrivastav (Jul 27, 2017 10:46 a.m.) (Question ID: 6970)

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Write balanced chemical equation for the following statements:

(i) NaOH solution is heated with zinc granules.

(ii) Excess of carbon dioxide gas is passed through lime water.

(iii) Dilute sulphuric acid reacts with sodium carbonate.

(iv) Egg shells are dropped in hydrochloric acid.

(v) Copper (II) oxide reacts with dilute hydrochloric acid.

Posted by Vivek Kr (Jul 27, 2017 9:21 a.m.) (Question ID: 6969)

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  • (i)2NaOH(aq) + Zn(s) -> Na2ZnO2  + H2(g)

    (ii)  CO2 + Ca(OH)2 -> CaCO3 (milky)+H2

     CaCO3 + H2O +CO2 -> Ca (HCO3)2 (milkiness disappears)

    (iii) H2SO4 + Na2CO3 -> Na2SO4 + H2O +CO2

    (iv) CaCO3 + 2HCl -> CaCl2 +H2O+CO2

    (v) CuO + 2HCl ->  CuCl2 + H2O

    Answered by Chanika Bhambri (Jul 27, 2017 2:14 p.m.)
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Full form of DVC.

Posted by Arpan Bhowmick (Jul 27, 2017 8:35 a.m.) (Question ID: 6968)

  • Damodar Valley Corporation

    Posted by Nitin Upadhyay (Jul 27, 2017 11:39 a.m.)
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  • Damodar Valley Corporation

    Answered by Nitin Upadhyay (Jul 27, 2017 12:16 p.m.)
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Which phrases did the narrator use to describe the arrival of the night ?

Posted by Amit Tyagi (Jul 27, 2017 6:46 a.m.) (Question ID: 6967)

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Can we use cramer rule to solve determinant questions in board exams as it is not given in ncert book? ? ? 

Posted by Pushpendra Singh (Jul 27, 2017 1:48 a.m.) (Question ID: 6966)

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  • its not cramer rule its cremer rule or cross multiplication method which is the most easiest way to solve LE in 2 variables and it is given in ncert book if not your book has some problem  or you have it

    Answered by Vighnesh 007 (Jul 27, 2017 6:09 p.m.)
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A body moves with velocity 5m/s under acceleration 2m/s find the time taken to travel a distance of 20m???

Posted by Farhan Akhter (Jul 27, 2017 1:45 a.m.) (Question ID: 6965)

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  • U=5

    a=2

    S=20

    Apply second eq of motion . 

    Answered by Pushpendra Singh (Jul 27, 2017 1:50 a.m.)
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ledger

Posted by Aniket Jain (Jul 27, 2017 12:42 a.m.) (Question ID: 6964)

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What were the most precious possession of Jim and Della 

Posted by Khans Khans (Jul 26, 2017 10:28 p.m.) (Question ID: 6963)

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The writer gives details of Jim's flat.pick out the details.

Posted by Khans Khans (Jul 26, 2017 10:27 p.m.) (Question ID: 6962)

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How did Della save her one dollar and eighty-seven cents?

Posted by Khans Khans (Jul 26, 2017 10:25 p.m.) (Question ID: 6961)

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Among magnesium silicon and aluminum.. Which has highest ionisation energy? 

 

Posted by Uttam Sur (Jul 26, 2017 10:12 p.m.) (Question ID: 6960)

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  • Ionization enthalpy is the energy required to remove the most loosely bound electron from an isolated atom (in the gaseous state) for one mole of an element.

    Among magnesium, silicon and aluminum, silicon has highest ionisation energy. Magnesium, aluminum and silicon are the elements of the third period in the periodic table. As one moves from left to right in the periodic table, there is a regular increase in the magnitude of ionization enthalpy of elements, with a few exceptions. E.g. The ionization enthalpy of Al (aluminium) is lower than that of Mg (magnesium). The first ionization enthalpy of magnesium is higher because the electron is removed from the fully filled 's' orbital.

    The first ionisation enthalpies of magnesium, aluminum and silicon are given below:-

    Period  Element First ionisation enthalpy Element First ionisation enthalpy Element First ionisation enthalpy
    3  Magnesium  737 kJ mol-1 Aluminum 577 kJ mol-1 Silicon 786 kJ mol-1
    Answered by Gurjeet Singh (Jul 26, 2017 10:55 p.m.)
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How does the law of DMU affect the law of demand?

Posted by Sailja Dammani (Jul 26, 2017 9:29 p.m.) (Question ID: 6959)

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  • Law of DMU states that as we consume more and more unit of a particular commodity each successive unit give lesser and lesser satisfaction so as the consumer demand more quantity of a particular commodity utility from it falls which is a reason that consumer value extra units at a lesser price.

      

    Answered by Lakshay Sharma (Jul 26, 2017 11:19 p.m.)
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What is ment by biological magnification

Posted by Syed Azim (Jul 26, 2017 9:10 p.m.) (Question ID: 6958)

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  • The increase in the concentration of a toxicant at successive higher trophic levels.

    Answered by Dr Pathikrt Banerjee (Jul 27, 2017 5:46 p.m.)
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  • 1. Biological magnification is also known as Biomagnification.

    2. It is the increase in concentration of certain chemicals like pesticides (ex. DDT) and heavy metals (ex. Mercury) in the tissue of living being at each successive level of food chain.

    3. The concentration of these chemicals is highest in the top trophic level.

    Answered by Nitin Upadhyay (Jul 27, 2017 11:50 a.m.)
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In chapter introduction to trignometry how we will know where we have to which formula

 

Posted by Prabhat Mahto (Jul 26, 2017 9:03 p.m.) (Question ID: 6957)

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  • understand the concpt apply it

    Answered by Vighnesh 007 (Jul 27, 2017 6:15 p.m.)
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What is the integration of under root sinx

Posted by Vikas Thakur (Jul 26, 2017 8:28 p.m.) (Question ID: 6956)

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http://mycbseguide.com/downloads/cbse-class-12-geography/1863/cbse-important-questions/6/

Is this for 2017-18?because I'm learning these imp ques only for boards exams 

 

Posted by Shrey Roy (Jul 26, 2017 7:12 p.m.) (Question ID: 6955)

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