Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 6

Q: 17. A sample of drinking water was found to be severely contaminated with chloroform, Equation , 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 Equation parts.

∴Mass percent of 15 ppm chloroform in water

Equation

Equation

(ii) Equation of the sample contains Equation

Equation

Equation

Molar mass of Equation

Equation

∴ Molality of chloroform in water Equation

Equation

Q: 18 Express the following in the scientific notation:

(i) Equation

(ii) Equation

(iii) 8008

(iv) Equation

(V) Equation

Answer:

(i) Equation

(ii) Equation

(iii) Equation

(iv) Equation

(v) Equation

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

(i) Equation

(ii) 208

(iii) 5005

(iv) Equation

(v) 500.0

(vi) Equation

Answer:

(i) Equation

There are 2 significant figures.

(ii) Equation

There are 3 significant figures.

(iii) Equation

There are 4 significant figures.

(iv) Equation

There are 3 significant figures.

(v) Equation

There are 4 significant figures.

(vi) Equation

There are 5 significant figures.

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