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).

This structure is hydrogen bonding for water ethanol

Structure of Ethanol and Water

This structure is hydrogen bonding for water ethanol

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 ?

A carbon-12 atom is made up of six protons and six neutrons,

Structure of Carbon Atoms

A carbon-12 atom is made up of six protons and six neutrons,

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?

There are three rules on determining how many significant figures

Structure of Significant Figures

There are three rules on determining how many significant figures

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 mass and abundance

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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