Class 12 Exam  >  Class 12 Questions  >  5.25% solution of a substance is isotonic wit... Start Learning for Free
5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will be
  • a)
    90g mol-1
  • b)
    115g mol-1
  • c)
    105g mol-1
  • d)
    246 g mol-1
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
5.25% solution of a substance is isotonic with a 21 .5% solution of ur...
View all questions of this test
Most Upvoted Answer
5.25% solution of a substance is isotonic with a 21 .5% solution of ur...
Given:
- A 5.25% solution of a substance is isotonic with a 21.5% solution of urea (NH2CONH2) by weight of solution in the same solvent at 300 K.
- The densities of both the solutions are assumed to be equal to 1.0 g cm-3.

To find: Molar mass of the substance

Solution:
Isotonic solutions are those that have the same osmotic pressure, which means that they have the same concentration of solute particles per unit volume. In this case, the 5.25% solution of the substance and the 21.5% solution of urea have the same osmotic pressure.

Step 1: Calculate the mole fraction of urea in the 21.5% solution.
The weight percentage of urea in the solution is 21.5%, which means that 100 g of the solution contains 21.5 g of urea and 78.5 g of the solvent. The number of moles of urea can be calculated as:
n(urea) = (21.5 g)/(60.06 g/mol) = 0.358 mol
The number of moles of solvent (water) can be calculated as:
n(solvent) = (78.5 g)/(18.015 g/mol) = 4.36 mol
The mole fraction of urea in the solution is:
X(urea) = n(urea)/(n(urea) + n(solvent)) = 0.076

Step 2: Calculate the mole fraction of the substance in the 5.25% solution.
Since the two solutions are isotonic, they have the same concentration of solute particles per unit volume. Therefore, the mole fraction of the substance in the 5.25% solution should be the same as the mole fraction of urea in the 21.5% solution. Thus,
X(substance) = X(urea) = 0.076

Step 3: Calculate the molecular weight of the substance.
The molecular weight of the substance can be calculated as:
M(substance) = (100 g)/(5.25 g/mol)/(6.02 x 10^23 molecules/mol) = 246 g/mol

Therefore, the correct answer is option D, 246 g/mol.
Explore Courses for Class 12 exam
5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer?
Question Description
5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? for Class 12 2024 is part of Class 12 preparation. The Question and answers have been prepared according to the Class 12 exam syllabus. Information about 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 12 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer?.
Solutions for 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? in English & in Hindi are available as part of our courses for Class 12. Download more important topics, notes, lectures and mock test series for Class 12 Exam by signing up for free.
Here you can find the meaning of 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer?, a detailed solution for 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? has been provided alongside types of 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice 5.25% solution of a substance is isotonic with a 21 .5% solution of urea (NH2CONH2 )by weight of solution in the same solvent at 300 K. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3 then, molar mass of the substance will bea)90g mol-1b)115g mol-1c)105g mol-1d)246 g mol-1Correct answer is option 'D'. Can you explain this answer? tests, examples and also practice Class 12 tests.
Explore Courses for Class 12 exam
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev