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. (i) Give two industrial applications of distillation under reduced pressure. (ii) Why is it necessary to use acetic acid and not hydrochloric acid for acidification of sodium extract for testing sulphur by lead acetate test?

Posted by Slr Teja (Feb 22, 2017 7:25 a.m.) (Question ID: 2427)

  • Answers:
  • Ans. (i)Distillation Under Reduced Pressure is used for purifying or separating thermally unstable liquid compounds.

    Uses :

    • In Petroleum Refining
    • in food processing

    (ii) For testing of sulphur present in the organic compound, the Lassaigne’s extract is acidified with acetic acid (CH3COOH) and not sulphuric acid because lead acetate is soluble and does not interfere with the test. If sulphuric acid (H2SO4 ) is used, lead acetate will react with H2SO4 itself to form white ppt. PbSO4.

    Answered by Naveen Sharma (Feb 22, 2017 12:01 p.m.)
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. Which species is the smallest aromatic substance?

Posted by Lokesh i47 (Feb 21, 2017 9:40 p.m.) (Question ID: 2411)

  • Answers:
  • The cyclopropenyl cation is the smallest aromatic substance.

    As to π electrons, when n = 0, the ordinary cyclopropene molecule is not aromatic. It becomes aromatic only if the third π electron is missing. That is, when it becomes the cyclopropenyl cation and its ring has a positive charge.

    Answered by Shweta Gulati (Feb 21, 2017 10:41 p.m.)
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IUPAC NAME OF CH3COCH2CH2CH2COOH

Posted by nilesh Kumar (Feb 17, 2017 4:33 p.m.) (Question ID: 2245)

  • Answers:
  • Ans. 5-oxohexanoic acid

    Answered by Naveen Sharma (Feb 17, 2017 5:13 p.m.)
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What is buffer solution

 

Posted by alol dubey (Feb 16, 2017 6 a.m.) (Question ID: 2183)

  • Answers:
  • Ans. A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it.

    A common example would be a mixture of ethanoic acid and sodium ethanoate in solution.

    Answered by Naveen Sharma (Feb 16, 2017 9:52 a.m.)
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explain haeber's process

Posted by Shreya Maity (Feb 15, 2017 7:14 p.m.) (Question ID: 2155)

  • Answers:
  • The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures:

    <dl> <dd>N2 + 3 H2 → 2 NH3     (Δ<i>H°</i> = −91.8 kJ) => (Δ<i>H°</i> = −45.8 kJ·mol−1)</dd> </dl>
    Answered by Shweta Gulati (Feb 15, 2017 9:33 p.m.)
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What is hydro 

Posted by kajal mor (Feb 14, 2017 11:46 a.m.) (Question ID: 2100)

  • Answers:
  • hydro what?? 

     

    Answered by yakshith k (Feb 17, 2017 7:51 p.m.)
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Describe the structure of benzene 

Posted by neha khan (Feb 13, 2017 11:27 p.m.) (Question ID: 2092)

  • Answers:
  • The usual structural representation for benzene is a six carbon ring (represented by a hexagon) which includes three double bonds. Each of the carbons represented by a corner is also bonded to one other atom. In benzene itself, these atoms are hydrogens. The double bonds are separated by single bonds so we recognize the arrangement as involving conjugated double bonds. An alternative symbol uses a circle inside the hexagon to represent the six pi electrons. Each of these symbols has good and bad features. We'll use the three double bond symbol simply because it is also routinely used in the text.

    <center>

    </center>

    Keep in mind that if the hexagon contains neither the three double bonds nor the circle, the compound is not aromatic. It is simply cyclohexane and there are two hydrogens on each carbon atom. This is easy to mistake when hurrying, so be careful when you are intepreting any structural formulas which include hexagons.

    <center>

    </center>
    Answered by Vikrant Singh (Feb 14, 2017 11:09 a.m.)
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What is inert pair effect?

Posted by Bhanupriya SAHU (Feb 11, 2017 9:50 p.m.) (Question ID: 2021)

  • Thanks Naveen sharma

    Posted by Bhanupriya SAHU (Feb 12, 2017 12:02 a.m.)
  • Thanks rima

    Posted by Bhanupriya SAHU (Feb 12, 2017 12:01 a.m.)
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  • Answers:
  • In short,  the inert pair effect is a tendency of the electrons in the outermost atomic s orbital to remain unionized or unshared in compounds of post -transition metals .

    Answered by RIMA PAUL (Feb 11, 2017 10:54 p.m.)
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  • Ans. Group 13 elements have ns2np1 electronic configuration. Hence they would be expected to be trivalent. In most of their compounds this is the case, however for the heavy elements lower oxidation states are more stable. Group 13 elements have ns2np1 electronic configuration. Hence they would be expected to be trivalent. In most of their compounds this is the case, however for the heavy elements lower oxidation states are more stable. This is explained by the s electrons remaining paired and not participating in bond formation. This inertness of s-subshell electrons towards the bond formation is called inert pair effect. This happens because the s orbitals are held closer to the nucleus, therefore the electrons present in s orbitals are held strongly by nucleus because of large electrostatic forces. Hence the energy required to unpair the s-electrons is high because of which they remain paired.

    This is explained by the s electrons remaining paired and not participating in bond formation. This inertness of s-subshell electrons towards the bond formation is called inert pair effect.

    This happens because the s orbitals are held closer to the nucleus, therefore the electrons present in s orbitals are held strongly by nucleus because of large electrostatic forces.

    Hence the energy required to unpair the s-electrons is high because of which they remain paired.

    Answered by Naveen Sharma (Feb 11, 2017 10:45 p.m.)
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Give examples of intramolecular hydrogen bonding 

Posted by Ashish Sidhu (Feb 08, 2017 10:14 a.m.) (Question ID: 1908)

  • Answers:
  • Ans. 
    When the hydrogen bond is present between two atoms of the same molecule, then it is known as intramolecular hydrogen bond.

    <font color="#262626" face="q_serif, Georgia, Times, Times New Roman, serif">For example, intramolecular hydrogen bonding occurs in ethylene glycol (C2H4(OH)2) between its two hydroxyl groups due to the molecular geometry.</font>

    Answered by Naveen Sharma (Feb 08, 2017 11 a.m.)
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  • When the hydrogen bond is present between two atoms of the same molecule, then it is called as intramolecular hydrogen bond.

    Eg. In the above image, the dotted line represents the intramolecular bonding between hydrogen and oxygen of the same molecule.

    Answered by Shweta Gulati (Feb 08, 2017 10:37 a.m.)
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what are heat capacities at constant volume and pressure?

 

Posted by bhumika Upadhyay (Feb 01, 2017 10:53 a.m.) (Question ID: 1734)

  • Answers:
  • Ans. The heat capacity of anything tells us how much heat is required to raise a certain amount of it by one degree. For a gas we can define a molar heat capacity C - the heat required to increase the temperature of 1 mole of the gas by 1 K.

    Q = nCT

     

    The value of the heat capacity depends on whether the heat is added at constant volume, constant pressure, etc.

    CV, the heat capacity at constant volume, and CP, the heat capacity at constant pressure.

    <h4>Heat Capacity at Constant Volume CV</h4>

    Q = nCVΔT

    For an ideal gas, applying the First Law of Thermodynamics tells us that heat is also equal to:

    Q = ΔEint + W, although W = 0 at constant volume.

    <h4>Heat Capacity at Constant Pressure: </h4>

    For an ideal gas at constant pressure, it takes more heat to achieve the same temperature change than it does at constant volume. At constant volume all the heat added goes into raising the temperature. At constant pressure some of the heat goes to doing work.

    Q = nCPΔT

    For an ideal gas, applying the First Law of Thermodynamics tells us that heat is also equal to:

    Q = ΔEint + W

    At constant pressure W = PΔV = nRΔT

    Answered by Naveen Sharma (Feb 01, 2017 12:17 p.m.)
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What is hyper conjugation?

Posted by Anju Bakshi (Jan 29, 2017 8:29 p.m.) (Question ID: 1678)

  • Answers:
  • Ans. Hyperconjugation is the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system.

    Answered by Naveen Sharma (Jan 29, 2017 9:39 p.m.)
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What is the difference between polar and non polar covalent bonds?

Posted by Gurdev Kaur (Jan 29, 2017 6:58 p.m.) (Question ID: 1672)

  • Answers:
  • Polar covalent bond means there is electronegativity difference in the atoms forming covalent bond.for example HCI, H is electropositive in nature whereas Cl is electronegative .

    Non polar covalent bond means there is no electronegativity difference between the atoms forming covalent bond.for example Cl2 

    Answered by shruti dadhwal (Jan 30, 2017 7:42 a.m.)
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  • Ans. Polar covalent bonding is a type of chemical bond where a pair of electrons is unequally shared between two atoms. In a polar covalent bond, the electrons are not equally shared because one atom spends more time with the electrons than the other atom. In polar covalent bonds, one atom has a stronger pull than the other atom and attracts electrons. e.g. H2O

    Nonpolar covalent bonds are a type of bond that occurs when two atoms share a pair of electrons with each other. These shared electrons glue two or more atoms together to form a molecule. e.g. Cl2

    Answered by Naveen Sharma (Jan 29, 2017 10:02 p.m.)
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Calculate the mass of 1 molecule of O3 and Na

 

Posted by Inderpreet Kour (Jan 26, 2017 1:25 p.m.) (Question ID: 1609)

  • Answers:
  • 1) 1mole of O3 weighs 48g. 1mole contains 6.022*10^23 molecules.

    So 1molecule of O3 weighs  (48*1)/6.022*10^23 g. =7.97*10^-23g.

    2) 1 mole of Na weighs 23g. The same way,

    1molecule of Na weighs (23*1)/6.022*10^23 g. =3.81*10^-23g.

    Answered by yakshith k (Feb 17, 2017 7:58 p.m.)
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IUPAC name of compound CH3-O-CH2-O-CH2-CH2-O-CH3

Posted by Jyoti kumari (Jan 23, 2017 10:52 p.m.) (Question ID: 1579)

  • Answers:
  • Sorry : Correct name is 1-Methoxy-2-(MethoxyMethoxy)Ethane
     

    Answered by Naveen Sharma (Jan 24, 2017 6:32 p.m.)
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  • Solution : IUPAC Name of compound CH3-O-CH2-O-CH2-CH2-O-CH3 is 1-methoxy-2-(2-methoxymethoxy)ethane. 

    Answered by Payal Singh (Jan 24, 2017 5:09 p.m.)
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  • Ans. 1-Methoxy-2-(2-MethoxyMethoxy)Ethane

    Answered by Naveen Sharma (Jan 24, 2017 4:54 p.m.)
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electrode potential

Posted by Bhargab Talukdar (Jan 22, 2017 2:14 a.m.) (Question ID: 1527)

  • Answers:
  • Electrode potential, <i>E</i>, in chemistry or <a href="https://en.wikipedia.org/wiki/Electrochemistry" title="Electrochemistry">electrochemistry</a>, according to a <a href="https://en.wikipedia.org/wiki/IUPAC" title="IUPAC">IUPAC</a> definition,<a href="https://en.wikipedia.org/wiki/Electrode_potential#cite_note-1">[1]</a> is the <a href="https://en.wikipedia.org/wiki/Electromotive_force" title="Electromotive force">electromotive force</a> of a<a href="https://en.wikipedia.org/wiki/Galvanic_cell" title="Galvanic cell">cell</a> built of two <a href="https://en.wikipedia.org/wiki/Electrode" title="Electrode">electrodes</a>:

    • on the left-hand side is the <a href="https://en.wikipedia.org/wiki/Standard_hydrogen_electrode" title="Standard hydrogen electrode">standard hydrogen electrode</a>, and
    • on the right-hand side is the electrode the potential of which is being defined.

    By <a href="https://en.wikipedia.org/wiki/Convention_(norm)" title="Convention (norm)">convention</a>:

    <dl> <dd><i>E</i>Cell = <i>E</i>Cathode − <i>E</i>Anode</dd> </dl>

    From the above, for the cell with the <a href="https://en.wikipedia.org/wiki/Standard_hydrogen_electrode" title="Standard hydrogen electrode">standard hydrogen electrode</a> (potential of 0 by convention), one obtains:

    <dl> <dd><i>E</i>Cell = <i>E</i>Right − 0 = <i>E</i>Electrode</dd> </dl>

    The left-right convention is consistent with the international agreement that redox potentials be given for reactions written in the form of reduction half-reactions.

    Electrode potential is measured in <a href="https://en.wikipedia.org/wiki/Volt" title="Volt">volts</a> (V).

    Answered by yakshith k (Jan 23, 2017 6:40 p.m.)
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  • Electrode potential is defined as the potential of a cell consisting of the electrode in question acting as a cathode and the standard hydrogen electrode acting as an anode. Reduction always takes place at the cathode, and oxidation at the anode.

    Answered by Vikrant Singh (Jan 22, 2017 8:04 a.m.)
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How can you explain higher stability of BCl3 as compared to TlCl3

Posted by Shadab Mahmood (Jan 17, 2017 11:48 a.m.) (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 12:40 p.m.)
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What is the active mass of water

 

Posted by Sajal Jain (Jan 15, 2017 10:28 a.m.) (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 5:04 p.m.)
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Nacl is soluble in water and insoluble in petrol why?

 

Posted by Udit Vaibhav (Jan 13, 2017 11:35 p.m.) (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 10 p.m.)
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  • 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 11:58 p.m.)
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Why lithium halides are somewhat covalent?

Posted by Bikash Adhikari (Jan 13, 2017 8:37 a.m.) (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 10:41 a.m.)
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What ie photoelectric effect

Posted by Rajnish Singh (Jan 12, 2017 11:09 a.m.) (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 11:58 a.m.)
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  • 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 11:58 a.m.)
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Why is Ga smaller in size than Al? 

Posted by Hitesh Saini (Jan 07, 2017 8:40 a.m.) (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 6:51 p.m.)
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how hydrogen is different from halogens?

 

Posted by Muskan Goyal (Jan 04, 2017 12:57 p.m.) (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 8:08 p.m.)
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Why does the colour of NaCl chage into blue whe we add some lemon juice? 

 

Posted by Kirtti RANJAN MISHRA (Jan 03, 2017 9:35 p.m.) (Question ID: 1054)

Why the salts of superoxides are coloured?

Posted by Bibhu Mukhopadhyay (Jan 01, 2017 3 p.m.) (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 10:33 p.m.)
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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 12:09 p.m.) (Question ID: 977)

What is polarity

 

Posted by piyush jain (Dec 28, 2016 10:31 p.m.) (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 9:12 p.m.)
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  • 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 11:36 a.m.)
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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 11:35 a.m.) (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 6:12 p.m.)
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What do you mean by hydride gap?

Posted by Athira Shaji (Dec 23, 2016 10:38 a.m.) (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 2:14 p.m.)
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  • 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 11:15 a.m.)
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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 10:57 p.m.) (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 11:13 p.m.)
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Calculate pH for 0.001M NaOH

Posted by Medha Krishna (Dec 14, 2016 6:57 p.m.) (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 8:51 p.m.)
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