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what is mean by 3r's princilples in the context of use of plastics



Posted by Larissa D'mello (May 29, 2017 10:09 p.m.) (Question ID: 5569)

  • Answers:
    • Reuse
    • Reduce
    • Recycle
    Answered by Payal Singh (May 29, 2017 10:47 p.m.)
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Write balanced chemical equation that takes place during respiration?

Posted by Rishabh Singhal (May 29, 2017 8:02 p.m.) (Question ID: 5568)

  • Answers:
  • C6H12O6 + 6O2 {tex}\to {/tex} 6CO2 + 6H2O + Energy It is exothermic reaction because a large amount of heat ie released.

    Answered by Payal Singh (May 29, 2017 9:20 p.m.)
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Pens are sold in a pack of 8 and notepads are sold in a pack of 12.Find the least number of pack of each type that one should buy so that there are equal number of pen and notepads 2014


Posted by Viswa Viswesh (May 29, 2017 7:54 p.m.) (Question ID: 5567)

  • Answers:
  • No of pens in a pack = 8 

    No of notepads in a pack = 12

    Prime factor of 8 = {tex}2\times 2\times 2 = 2^3{/tex}

    Prime factor of 12 = {tex}2 \times 2 \times 3 = 2^2 \times 3{/tex}

    LCM (8,12) = {tex}2^3 \times 3 = 24 {/tex}


    Therefore, 24 is the least number of packets one must get

    Answered by Payal Singh (May 29, 2017 9:15 p.m.)
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give the iupac name of [CrCl2(en)2]Cl where en=ethane-1,2-diamine

Posted by srinivas chandra (May 29, 2017 6:17 p.m.) (Question ID: 5566)

  • Answers:
  • Dichloridobis-ethylenediamine Chromium(III)Chloride.

    Answered by Payal Singh (May 29, 2017 6:28 p.m.)
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illustrate kolbe's reaction and williamson synthesis with chemical equation?

Posted by srinivas chandra (May 29, 2017 6:15 p.m.) (Question ID: 5565)

  • Answers:
  • Kolbe's reaction: When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon dioxide, followed by acidification, undergoes electrophilic substitution to give ortho-hydroxybenzoic acid as the main product.

    This reaction is known as Kolbe's reaction.

    [Add image Here] 

    Williamson ether synthesis: Williamson ether synthesis is a laboratory method to prepare symmetrical and unsymmetrical ethers by allowing alkyl halides to react with sodium alkoxides.

    [Add image here]

    This reaction involves SN2 attack of the alkoxide ion on the alkyl halide. Better results are obtained in case of primary alkyl halides.

    [Add image here]


    If the alkyl halide is secondary or tertiary, then elimination competes over substitution.


    Answered by Payal Singh (May 29, 2017 6:32 p.m.)
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formula of magnesium nitrite

Posted by Neeraj Neeraj (May 29, 2017 5:18 p.m.) (Question ID: 5564)

  • Answers:
  • Mg(NO3)2

    Answered by Payal Singh (May 29, 2017 5:43 p.m.)
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Posted by amit kumar sinha (May 29, 2017 5:11 p.m.) (Question ID: 5563)

  • Answers:
  • Nutrients are substancesNutrients are substances that are required for the nourishment of organism while nutrition is the entire process by which organisms obtain energy and nutrients from food.

    Answered by Payal Singh (May 29, 2017 5:46 p.m.)
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How did industrialisation give birth to imperilism?


Posted by Vaibhavi Roy (May 29, 2017 4:39 p.m.) (Question ID: 5562)

  • Answers:
  • 19th century was marked by Industrialisation resulting in rapid socio , economic changes characterised by technological developments, inventions bringing about change from a domestic system to a factory system.

    It is identified with the establishment with factories, industries , rise of industrial labour force.Factories, industries were set up on a large scale, there was a rise of industrial labour.

    With the development of trade and in the quest for expanding further trade ,many European powers set on an imperialistic conquest establishing full control over regions in Asia and Africa with the prospect of controlling those regions for economic gains.

    This helped them to establish control over natural resources of the smaller and weaker nations and to ensure supply of raw materials and goods and to expand market for their goods.

    Britain , France made vast overseas expedition in their greed for acquiring more and more colonies. It brought about dramatic changes in Asia and Africa. . For instance, Africa was demarcated and divided among the European colonists.

    Germany, Belgium , US also became colonial powers and expanded their influence.

    They also hired labours from colonies , With the growth in British industrial economy, the demand for labour further increased. The 19th century witnessed further changes in the labour pattern movement with the indentured labour migration from India, who went to work in plantations, mines , road and railways projects. They mainly migrated to the British controlled Caribbean islands.

    Colonialism also helped in expanding further trade and provided ready markets for goods manufactured in Europe, further accelerating production in Europe

    Answered by Naveen Sharma (May 29, 2017 4:50 p.m.)
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Advantages of using graphs to study motion.

Posted by Ankush Tarafdar (May 29, 2017 4:03 p.m.) (Question ID: 5561)

  • Answers:
  • The following are the advantages ofbgraphs:

    •  Instantaneous values of the velocity of the body at different periods of time can be found.
    • The distance (displacement actually) travelled can be found easily by calculating the area below the graph.
    • The acceleration can be found by slope of graph.
    Answered by Payal Singh (May 29, 2017 4:11 p.m.)
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Why do leaves fall in autumn only?Why not in other seasons?

Posted by Rachna gupta (May 29, 2017 2:05 p.m.) (Question ID: 5560)

  • Answers:
  • As winters ends and autumn begins, the days get shorter and shorter. With fewer daylight hours, leaves are not able to make as much chlorophyll as they can during the long daylight hours of spring and summer. As the chlorophyll fades, we are able to see other colors, such as orange and yellow.

    Many people mistakenly believe that weather makes leaves change color. While this is not true, weather can affect how vibrantly the colors appear.

    If the weather is too hot or cold, the leaves will not be as bright as they begin to change. The best weather for brilliant autumn foliage is sunny, warm days and cool nights.

    Water also plays an important role in autumn. If a tree doesn't receive enough water, the leaves will die faster and fall to the ground. If there is too much rain the tree won't receive enough sunlight, and the leaves will not be brightly colored.

    Answered by Shivam .G (May 29, 2017 4:21 p.m.)
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Why do we have two kidneys?

Posted by Rachna gupta (May 29, 2017 2:05 p.m.) (Question ID: 5559)

  • Answers:
  • Two kidneys can effectively remove waste materials from the blood and to control the amount of water absorbed and the amount passed to the urinary bladder for excretion in the form of urine.​

    If one fails by any reason, then the other can maintain the function, so that waste doesnot accumulate within the body. This is the advantage of having two kidneys.


    Symmetry. Having one that balances the other is simply a better design than a single one located either right or left. The center of the human body is already occupied.

    Answered by Payal Singh (May 29, 2017 3:02 p.m.)
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Nylon is prepared from simple chemicals obtained from _____________

Posted by Anandan Radhakrishnan (May 29, 2017 1:21 p.m.) (Question ID: 5558)

Polythene is prepared from __________

Posted by Anandan Radhakrishnan (May 29, 2017 1:20 p.m.) (Question ID: 5557)

  • Answers:
  • Ethene 

    Answered by Payal Singh (May 29, 2017 1:22 p.m.)
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Let f is a function from X to Y.  define a relation R in X given by R = {(a, b) :f(a) = f(b)}.  show tha R is an equivalence relation

Posted by yatin jindal (May 29, 2017 12:14 p.m.) (Question ID: 5556)

  • Answers:
  • Ans. Equivalence relation are Relations which are reflexive, transitive and symmetric.

    R = {(a, b): f(a) = f(b)}

    Check reflexive :

    Since f (a) = f (a),
    (a, a) ∈ R,
    Hence, R is reflexive.

    Check symmetric:

    If f (a) = f (b), then f (b) = f (a)
    Hence, (b, a) ∈ R.

    So, if (a, b) ∈ R
    then (b, a) ∈ R.
    R is symmetric.

    Check transitive :
    If (a, b) ∈ R
    ⇒ f(a) = f(b)    ........... (1)
    Also if, (b, c)∈ R
    ⇒ f(b) = f(a)  .................(2)

    From (1) & (2)
    f(a) = f(c)
    ⇒ (a, c) ∈ R,
    If (a, b) ∈ R & (b, c) ∈ R ,

    then (a, c) ∈ R

    R is transitive.

    Hence, R is an equivalence relation.

    Answered by Naveen Sharma (May 29, 2017 3:42 p.m.)
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I am facing problem in data handling,how can I solve my problems with this chapter


Posted by Bhairab Borah (May 29, 2017 11:33 a.m.) (Question ID: 5555)

  • Answers:
  • Refer videos on cbse guide app .They explain each and every concept clearly. You will surely built interest in the topic by watching those videos.

    Hope it helps!

    Thank you.

    Answered by Rachna gupta (May 29, 2017 2:04 p.m.)
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I pass 12th this year with five subject but fail in bio what should i do please help

Posted by Devesh Shukla (May 29, 2017 11:15 a.m.) (Question ID: 5554)

Summary of the whole novel 'The Story of My Life'...

Posted by Sejal Yadav (May 29, 2017 8:50 a.m.) (Question ID: 5553)

Vapour pressure of water is 360 mm Hg, how much urea should be added to 200ml water to reduce its vapour pressure by 0.5%?

Posted by Anayat Usain (May 29, 2017 1:49 a.m.) (Question ID: 5552)

  • Answers:
  • Vapour pressure of pure water, p= 360 mm Hg

    Lowered vapour pressure, p = 360 –0 .5% of 360

    = 360 – 1.8 = 358.2 mm Hg

    Now, Weight of water, w1= 200ml x 1g.ml = 200g

    Weight of urea w2 = ?

    Molecular weight of water, M1 = 18 g/mol Molecular weight of urea, M2 = 60 g/mol

    According to Roult’s law:


    {tex}{p^o -p \over p} = {n_2\over n_1 + n_2}{/tex}

    => {tex}{360 - 358.2\over 358.2} = { {w_2 \over M_2}\over {{w_1\over M_1 } + {w_2 \over M_2}}}{/tex}

    => {tex}0.005 = { {w_2 \over M_2}\over {{w_1\over M_1 } + {w_2 \over M_2}}}{/tex}

    => {tex}0.005 {\left ({w_1\over M_1 } + {w_2 \over M_2}\right )}= {w_2 \over M_2}{/tex}

    => {tex}0.005 \times {w_1\over M_1 } = {w_2 \over M_2} - 0.005\times {w_2 \over M_2}{/tex}

    => {tex}0.005 \times {w_1\over M_1 } =0.995\times {w_2 \over M_2}{/tex}

    => {tex}{0.005 \over 0.995} \times {w_1\times M_2\over M_1 } = {w_2 }{/tex}

    => {tex}{0.005 \over 0.995} \times {200\over 18 }\times 60 = {w_2 }{/tex}

    => w2 =  3.33g

    Hence, 3.33g urea should be added

    Answered by Payal Singh (May 29, 2017 12:03 p.m.)
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Please explain and clear me the examples 46,47,48,49 of ch1 12class maths ncert


Posted by Harsh Goyal (May 29, 2017 12:42 a.m.) (Question ID: 5551)

Why benzophenone does not undergo cannizaro reaction? 

Posted by Akanksha Tomar (May 29, 2017 12:20 a.m.) (Question ID: 5550)

  • Answers:
  • Benzophenone It is a ketone, so it does not undergo Canniyzaro's reaction. Without {tex}\alpha{/tex} -hydrogen, it cannot participate in aldol condensation.

    Answered by Payal Singh (May 29, 2017 6:33 a.m.)
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It is rightly said that any discrimination based simply on caste, colour, creed, nationality and language is barbarous. Prejudices impede fraternity . discuss the issue with reference to "The last lesson". 

Posted by Ritu Ghosh (May 28, 2017 9:26 p.m.) (Question ID: 5549)

Effect of endoparasites in human intestine

Posted by Murali Dharan (May 28, 2017 9:08 p.m.) (Question ID: 5548)

  • Answers:
  • since they are parasites they are depended on our digested food foe their growth and successive livings. they take some of our essential salts, water, nutrients, glucose, etc which are essential for our basic life processes. because of these we can suffer though various problems such as tiredness, sleeping sickness, etc.   


    Answered by Shivam .G (May 29, 2017 3:32 p.m.)
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chordata inclides?


Posted by kolluru chandini (May 28, 2017 9:01 p.m.) (Question ID: 5547)

  1. may i have a clear information about..... species, genus, family
  2. 2. how to remember the scientific names
Posted by kolluru chandini (May 28, 2017 8:56 p.m.) (Question ID: 5546)

  • Answers:
  • 1. there is a hiererchy that follows; 








    2. just write all the scientific names with their common names and read them as much as you can, everytime. i bet you will not forget all your life. thats the only way to learn them.

    Answered by Devanshu Agarwal (May 29, 2017 11:40 a.m.)
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 what are the functions of bowman's capsule and glomerulus in human excretory system?

Posted by Chandan Pradhan (May 28, 2017 8:39 p.m.) (Question ID: 5545)

  • Answers:
  • Glomerulus and Bowman's capsule does the work of filtration , it  filters the most of ions and the larger ions escape in this capsule


    Answered by Murali Dharan (May 28, 2017 9:13 p.m.)
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What do you mean by somatic,haploid and diploid cells?

Posted by Chandan Pradhan (May 28, 2017 8:36 p.m.) (Question ID: 5544)

  • Answers:
  • A somatic cell is any cell of the body except sperm and egg cells. Somatic cells are diploid, meaning that they contain two sets of chromosomes, one inherited from each parent.

    A haploid cell contains one complete set of chromosomes.Haploid cells are formed via the process of meiosis. Example: human haploid cell contains 23 chromosomes.

    A diploid cell contains two complete sets of chromosomes.Diploid cells are formed through mitosis.Example: human diploid cell contains 46 chromosomes.

    Answered by Payal Singh (May 29, 2017 7:53 a.m.)
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What is haemodialysis?

Posted by Chandan Pradhan (May 28, 2017 8:35 p.m.) (Question ID: 5543)

  • Answers:
  • Hemodialysis, also spelled haemodialysis, commonly called kidney dialysis or simply dialysis, is a process of purifying the blood of a person whose kidneys are not working normally.



    Answered by Payal Singh (May 29, 2017 11:25 a.m.)
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If the corresponding medians of two similar triangles are in the ratio 5:7 then find ratio of the corresponding sides?

Posted by Chandan Pradhan (May 28, 2017 8:35 p.m.) (Question ID: 5542)

  • Answers:
  • For similar triangles,

    Ratioof median=Ratio of sides


    Ratio of medians =5:7

    Answered by Payal Singh (May 29, 2017 7:54 a.m.)
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Describe the structure and functioning of nephron.

Posted by Chandan Pradhan (May 28, 2017 8:33 p.m.) (Question ID: 5541)

  • Answers:
  • Refer the nephron's para fully in book and write 6-7points with diagram

    Answered by Murali Dharan (May 28, 2017 9:15 p.m.)
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why and how are life processes maintained in our body

Posted by Harish Badhe (May 28, 2017 8:29 p.m.) (Question ID: 5540)

  • Answers:
  • Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:



    Transportation of substances




    Answered by Payal Singh (May 28, 2017 9:57 p.m.)
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