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

Question:

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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Comments

  • papa g
  • 2019-08-07 21:16:13

good


  • papa g
  • 2019-08-07 21:15:16

super


  • jasmeen
  • 2019-06-09 12:46:58

very much helpful


  • jasmeen
  • 2019-06-09 12:44:40

thanks


  • shanawaz
  • 2019-05-12 12:45:53

thanks all


  • RishAbh
  • 2019-04-14 06:56:34

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


  • Tarun raghav
  • 2018-06-14 23:46:29

Sukriya


Comment(s) on this Question

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....