A sample of drinking water was found to | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

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Academic session 2026-27, Chapter 1 in the current curriculum.

Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter Solutions. This page offers a step-by-step solution to the specific question from Exercise 2, Question 9:

A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):

(i) express this in percent by mass

(ii) determine the molality of chloroform in the water sample.

. With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 9:

A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):

(i) express this in percent by mass

(ii) determine the molality of chloroform in the water sample.

Answer:

1) 15 ppm means : 15 parts per million(106) of the solutions

So, Percent by mass = (mass of chloroform / total mass) x 100

= (15 / 106) x 100

= 1.5 x 10-3 %

 

2) Molality Mass of chloroform = 15 g

Molar mass of chloroform (CHCl3) = 1 × 12 + 1 × 1 + 3 × 35.5

= 119.5 g mol - 1

Moles of chloroform = 15 / 119.5 = 0.1255 mol

Mass of water = 106

Therefore molality = (moles of chloroform / mass of water ) x 1000

= (0.1255 / 106) x 1000

= 1.255 x 10-4 m


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NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

  • Read the question carefully and focus on the core concept being asked.
  • Reference examples and data from the chapter when answering questions about Solutions.
  • Review previous year question papers to get an idea of how such questions may be framed in exams.
  • Practice answering questions within the time limit to improve your speed and accuracy.
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Comments

  • papa g
  • Aug 07, 2019

good


  • papa g
  • Aug 07, 2019

super


  • jasmeen
  • Jun 09, 2019

very much helpful


  • jasmeen
  • Jun 09, 2019

thanks


  • shanawaz
  • May 12, 2019

thanks all


  • RishAbh
  • Apr 14, 2019

Y u haven't considered the weight of solvent in second part as (10^6-15) grams?


  • Tarun raghav
  • Jun 14, 2018

Sukriya


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Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 9: A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to....

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