Friday, 3 May 2013

H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.


H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.
Solution
given that
Molality =0.195 m,
Let take mass of solvent (water) = 1 kg 
Use above formula we get
Moles of solute = 0.195 mol
Molar mass of water (H2O ) = 2 × 1 + 16 = 18 

Mass of water (mass of solvent 1 kg = 1000 g
Number of moles of water = 1000 g / 18 = 55.56 mol
 
Use above formula we get

Mole fraction of H2S = 0.195/(0.195 + 55.56) = 0.0035
At STP, pressure (p) = 0.987 bar always
According to Henry’s law:
p = KH × X
KH  =  p / X   = 0.987 / 0.0035 = 282 bar
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28 comments:

  1. Sailesh Sinha7 August 2013 at 06:57

    p = KH.X p=partial pressure of the solute in vapor state above solution . 1bar = Ph20 + Ph2s . so the value of kh cant be right

    ReplyDelete
  2. Unknown4 May 2014 at 01:04

    This comment has been removed by the author.

    ReplyDelete
  3. Neeti11 January 2016 at 22:16

    How do we know that 0.195 is molality?

    ReplyDelete
    Replies
    1. Unknown8 September 2016 at 04:09

      in question it says 0.195m. m stands for molal, ie., molality

      Delete
    2. Unknown8 September 2016 at 04:19

      in question it says 0.195m. m stands for molal, ie., molality

      Delete
    3. Pankaj Mandal25 October 2017 at 04:27

      In question i.e 0.195 m is given where 'm' denotes the unit of molality.

      Delete
    4. anirudh lin dan20 February 2018 at 14:19

      m stands for molality😅🤗😊🤗😇

      Delete
    5. Unknown17 April 2019 at 08:17

      m is represented as molality and M is a symbol of milarity.

      Delete
    6. Unknown20 May 2019 at 01:23

      Small m is denoted molality when capital MI's denoted molarity

      Delete
    7. Unknown3 July 2019 at 06:55

      M stands for Molarity
      And m stands for molality

      Delete
  4. Unknown22 January 2016 at 23:48

    Bcoz it is written as 0.195m
    Here m might not be representing metre.
    Its a good question.

    ReplyDelete
  5. Unknown18 June 2016 at 23:14

    Pressure must be taken as 1.013 bar and the exact answer is 289.4 bar as per ncert text book..
    Last step is 1.013/0.0035 and the answer is 289.4

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    Replies
    1. Unknown8 September 2016 at 04:17

      are you sure? 0.987 is written at many places and really confused

      Delete
    2. Unknown8 September 2016 at 04:18

      are you sure?

      Delete
    3. Unknown19 April 2018 at 22:27

      Yes I think it's 1.01325 bar but in each n every book it is taken 0.987 bar

      Delete
  6. Kashish 😊😊10 April 2017 at 19:53

    Y is p at stp taken 0.987

    ReplyDelete
  7. utkarsh26 January 2018 at 08:28

    p = KH.X p=partial pressure of the solute in vapor state above solution . 1bar = Ph20 + Ph2s . so the value of kh cant be right

    ReplyDelete
  8. anirudh lin dan20 February 2018 at 14:22

    Why should we take 1kg of solvent?It is not mentioned in the question.

    ReplyDelete
  9. Unknown10 March 2018 at 09:07

    Molality is moles per kg so over here its 0.195 moles per 1 kg of solvent.

    ReplyDelete
  10. AKSINGH19 July 2018 at 03:00

    Thanks a lot well 1atm is equal to 1 bar or not

    ReplyDelete
  11. Unknown11 August 2018 at 22:10

    Thank you so much

    ReplyDelete
  12. Vrk9 December 2018 at 20:09

    Here all of these taken that 1 ATM means 0.987 bar but it is given in NCERT that 1 ATM means 1.013 bar why all these guys taken like this I don't understand

    ReplyDelete
    Replies
    1. Unknown30 May 2019 at 09:56

      I also not able to understand plzzz reply how come this

      Delete
  13. Unknown20 February 2019 at 07:44

    Since the solubility is given and pressure is also...so why cant we take s=kp

    ReplyDelete
  14. Anurag2 March 2019 at 08:01

    At s.t.p pressure is 1 atm which is 1.013 bar and not .987 bar please check your answer

    ReplyDelete
  15. Unknown2 August 2019 at 22:08

    Very helpful😊

    ReplyDelete

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