Chapter 13, Problem 59GQ

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# Concentrated aqueous ammonia has a molarity of 14.8 mol/L and a density of 0.90 g/cm3. What is the molality of the solution? Calculate the mole fraction and weight percent of NH3.

Interpretation Introduction

Interpretation: The weight percentage and mole fraction of NH3 are to be determined.

Concept introduction:

Mole fraction: Amount of that component divided by the total amount of all of the components of the mixture ( nA +  nB +  n...).

Mole fraction of A (χA)= nA nA +  nB +  n...

Weight percent: The mass of one component divided by the total mass of the mixture, multiplied by 100%

weight % A = Mass of A Mass of A + Mass of B + Mass of C + ...×100%

The number of moles of any substance can be determined using the equation

Numberofmole=GivenmassofthesubstanceMolarmass

Explanation

Given,

â€‚Â Molarity of aqueous ammonia solution is 14.8â€‰mol/L

â€‚Â Density of aqueous ammonia solution is 0.90â€‰g/cm3

â€‚Â Molar mass of ammonia is 17.03Â g/mol

â€‚Â Molar mass of water is 18.02Â g/mol

The number of moles of ammonia in 1â€‰L of solution, nammonia is 14.8â€‰moles

â€‚Â MassÂ ofÂ ammoniaâ€‰=â€‰numberâ€‰ofâ€‰molesâ€‰Ã—â€‰molarâ€‰mass=â€‰14.8â€‰molesâ€‰Ã—â€‰17.03Â g/molâ€‰=â€‰252.044â€‰g

Mass of ammonia solution is 0.90â€‰Ã—â€‰1000â€‰=â€‰900â€‰g

Mass of water is 900â€‰gâ€‰âˆ’â€‰251.6â€‰=â€‰684.4â€‰g

The number of moles of any substance can be determined using the equation

â€‚Â Numberâ€‰ofâ€‰moleâ€‰=Givenâ€‰massâ€‰ofâ€‰theâ€‰substanceMolarâ€‰massâ€‰

Number of moles of water is,

â€‚Â nwaterâ€‰=â€‰684

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