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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Chemistry
Chapter
Surface Chemistry

NTA Abhyas 2020 · Chemistry · Surface Chemistry

The qualitative sketches I, II and III given below show the...

The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of three different aqueous solutions of KCl, CH3OHC{H}_{3}OH and CH3(CH2)11OSO3−Na+C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+} at room temperature. The correct assignment of the sketches is -

The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of

Options

  1. AI:KCl,II:CH3OH,III:CH3(CH2)11OSO3−Na+I: KCl,II: C{H}_{3}OH,III: C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+}
  2. BI:CH3(CH2)11OSO3−Na+,II:CH3OH,III:KClI: C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+},II: C{H}_{3}OH,III: KCl
  3. CI:KCl,II:CH3(CH2)11OSO3−Na+,III:CH3OHI: KCl,II: C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+},III: C{H}_{3}OH
  4. DI:CH3OH,II:KCl,III:CH3(CH2)11OSO3−Na+I: C{H}_{3}OH,II: KCl,III: C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+}

Correct answer

D. I:CH3OH,II:KCl,III:CH3(CH2)11OSO3−Na+I: C{H}_{3}OH,II: KCl,III: C{H}_{3}{\left(C{H}_{2}\right)}_{11}OS{O}_{3}^{-}Na^{+}

Step-by-step solution

Water has large surface tension due to very strong interaction. Generally adding organic derivatives to water decreases its surface tension due to hydrophobic interaction.

In case III, hydrophobic interaction is stronger than case II causing surface tension to decrease more rapidly.

Due to K+Cl–K^{+}Cl^{–} (inorganic electrolyte) intermolecular forces increases, surface tension increases.
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