Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 10

Q: 29. Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is Equation .040 (assume the density of water to be one).

Answer:

Equation

Equation

Number of moles present in 1 L water:

Equation

Equation

Substituting the value of Equation in equation (1),

Equation

Equation

Equation

Equation

Equation

Equation Molarity of solution

Equation

Q: 30. What will be the mass of one Equation ?

Answer:

Equation mole of carbon atoms Equation atom of carbon

Equation

Equation

Equation of carbon.

Q: 31. How many significant figures should be present in the answer of the following calculation?

Equation Equation

(ii) Equation

(iii) Equation

Answer:

(1) Equation

Least precise number of calculation Equation

Equation Number of significant figures in the answer

Equation Number of significant figures in the least precise number

Equation

(ii) Equation

Least precise number of calculation Equation

Equation Number of significant figures in the answer = Number of significant figures in Equation

Equation

(iii) Equation

Since the least number of decimal places in each term is four, the number of significant figures in the answer is also 4.

Q: 32 Use the data given in the following table to calculate the molar mass of naturally occurring argon isotopes:

Data on isotopes

Isotope

Isotopic molar mass

Abundance

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Answer:

Molar mass of argon

Equation

Equation

Equation

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