# Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 6 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for CBSE/Class-7 : get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-7.

Q: 17. A sample of drinking water was found to be severely contaminated with chloroform, , supposed to be carcinogenic in nature. 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:

(i) 1 ppm is equivalent to 1 part out of 1 million parts.

∴ Mass percent of 15 ppm chloroform in water

(ii) of the sample contains

Molar mass of

∴ Molality of chloroform in water

Q: 18 Express the following in the scientific notation:

(i)

(ii)

(iii) 8008

(iv)

(V)

Answer:

(i)

(ii)

(iii)

(iv)

(v)

Q: 19 How many significant figures are present in the following?

(i)

(ii) 208

(iii) 5005

(iv)

(v) 500.0

(vi)

Answer:

(i)

There are 2 significant figures.

(ii)

There are 3 significant figures.

(iii)

There are 4 significant figures.

(iv)

There are 3 significant figures.

(v)

There are 4 significant figures.

(vi)

There are 5 significant figures.