• Home
  • NCERT Solutions
  • Class 12
  • Chemistry
  • Solutions
  • Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.

Benzene and toluene form ideal solution | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

Q38.

Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.

Molar mass of benzene(C6H6) = 6 X 12 + 6 X 1 = 78 g/mol

Molar mass of toluene = 7 x 12 + 8 x 1 = 92 g/mol

Now no of moles in 80g of benezen = 80 / 78 = 1.026 mol

No of moles in 100g of toluene = 100 / 92 = 1.087 mol

∴Mole fraction of benzene xb = 1.026 / 1.026 + 1.087 = 0.486

And Mole fraction of toluene,xt = 1 - 0.486 = 0.514

We have given that

Vapor pressure of pure benzene pb° = 50.71 mm Hg

And, vapour pressure of pure toluene, pt° = 32.06 mm Hg

Therefore partial Vapor pressure of benzene, pb = pb X xb

= 50.71 x 0.486

= 24.65 mm Hg

And partial Vapor pressure of toluene, pt = pt X xt

Pt = p°t X xt = 32.06 x 0.514

= 16.48

Total vapour pressure = 24.65 + 16.48 = 41.13 mm Hg

Mole fraction of benzene in vapour phase = 24.65 / 41.13 = 0.60

👍 0
👎 0
✍️ Add Answer
🚩 Report

Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

  • Read the question carefully and focus on the core concept being asked.
  • Reference examples and data from the chapter when answering questions about Solutions.
  • Review previous year question papers to get an idea of how such questions may be framed in exams.
  • Practice answering questions within the time limit to improve your speed and accuracy.
  • Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Important Questions & Answers

Why is this answer important for exams?

This question is important because it tests key concepts from the NCERT syllabus and is frequently asked in CBSE exams.

Which NCERT concept is used in this question?

This question is based on core NCERT concepts explained in the chapter and should be revised thoroughly before exams.

What is the correct answer to: Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.?

Molar mass of benzene(C6H6) = 6 X 12 + 6 X 1 = 78 g/mol

Molar mass of toluene = 7 x 12 + 8 x 1 = 92 g/mol

Now no of moles in 80g of benezen = 80 / 78 = 1.026 mol

No of moles in 100g of toluene = 100 / 92 = 1.087...

How do you solve Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene. step by step?

Step-by-step explanation:
• Molar mass of benzene(C6H6) = 6 X 12 + 6 X 1 = 78 g/mol

• Molar mass of toluene = 7 x 12 + 8 x 1 = 92 g/mol

• Now no of moles in 80g of benezen = 80 / 78 = 1

What common mistakes should be avoided in this question?

Students often lose marks by skipping steps, writing incomplete explanations, or misunderstanding keywords used in the question.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Smart Questions to Ask in a Parent-Teacher Meeting | PTM Made Easy

Smart Questions to Ask in a Parent-Teacher Meeting | PTM Made Easy

Parent-Teacher Meetings (PTMs) are more than quick updates on marks — they’re a chance to build a real partnership between home and school. A good Parent-Teacher Meeting conversation helps parents see beyond grades. It opens up insights about a child’s strengths, struggles, emotions and even hidden talents. When parents participate actively, they don’t just track […]

Read More
The Secret to Smarter Learning — Building Strong Critical Thinking Skills

The Secret to Smarter Learning — Building Strong Critical Thinking Skills

In today’s world of endless information , knowing how to think is more important than knowing what to think . From school projects to real – life decisions , critical thinking helps students question ideas , analyze facts and form logical conclusions . But what exactly does critical thinking mean ? Simply put , it’s […]

Read More
Study Smarter, Not Harder: Build Productive Habits That Stick

Study Smarter, Not Harder: Build Productive Habits That Stick

Every student dreams of better grades , stronger focus and more study time – but the real challenge isn’t starting, it’s staying consistent . Building productive study habits is not about studying all day , it’s about studying smart . In today’s fast – paced digital world, distractions are everywhere – from endless phone notifications […]

Read More
The Hidden Risks of Online Gaming for Children — Is your child safe while gaming online?

The Hidden Risks of Online Gaming for Children — Is your child safe while gaming online?

Online gaming has rapidly become one of the most popular pastimes among children. Whether it’s multiplayer mobile games , PC adventures or console challenges , kids are spending more time than ever in the virtual world . On the surface, gaming seems entertaining and even educational – improving hand- eye coordination , teamwork and problem […]

Read More

Student Discussion

Istupid
Class · · , · Mar 11, 2019
This is the most straight forward method possible. ᕕ(ಥʖ̯ಥ)ᕗ
👍 👎 Reply
Nitik
Class · · , · Jan 16, 2019
It's do long and difficult so tell any other way to solve it
👍 👎 Reply
Hemu
Class · · , · Jul 21, 2018
Any more Satisfactory way to solve
👍 👎 Reply

ADD NEW COMMENT

        Can’t find your school? Type full name and submit.