The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the vapour phase.
It is given that:
PAo = 450 mm of Hg
PBo = 700 mm of Hg
ptotal = 600 mm of Hg
From Raoult's law, we have:
ptotal = PA + PB
Therefore, xB = 1 - xA
= 1 - 0.4
= 0.6
Now, PA = PAo xA
= 450 × 0.4
= 180 mm of Hg
and PB = PBo xB
= 700 × 0.6
= 420 mm of Hg
Now, in the vapour phase: Mole fraction of liquid A = PA / (PA + PB )
=180 / (180+420)
= 180/600
= 0.30
And, mole fraction of liquid B = 1 - 0.30
= 0.70
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
| Experiment |
A/ mol L - 1 |
B/ mol L - 1 |
Initial rate/mol L - 1 min - 1 |
| I | 0.1 | 0.1 |
2.0 × 10 - 2 |
| II | -- | 0.2 |
4.0 × 10 - 2 |
| III | 0.4 | 0.4 | -- |
| IV | -- | 0.2 |
2.0 × 10 - 2 |
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:
It is given that:
PAo = 450 mm of Hg
PBo = 700 mm of Hg
ptotal = 600 mm of Hg
From Raoult's law, we have:
ptotal = PA + PB
Therefore, xB = 1 - xA
= 1 - 0.4
= 0.6
&nb...
Step-by-step explanation:
• It is given that:
•
• PAo = 450 mm of Hg
•
• PBo = 700 mm of Hg
This question is important because it tests key concepts from the NCERT syllabus and is frequently asked in CBSE exams.
This question is based on core NCERT concepts explained in the chapter and should be revised thoroughly before exams.
Students often lose marks by skipping steps, writing incomplete explanations, or misunderstanding keywords used in the question.
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Student Discussion
p(total)=p(a)+p(b) which is p°(a)x(a)+p°(b)x(b)
But we also know that sum of mole fractions is 1 x(b)=1-x(1)
Deducing it we get the simpler form
Ask something good baby...
By using the formula P(total)=P(A)+[P(B)-P(A)]X(B), we get the value of X(B) as 0.42 and X(a) as 0.58. If done in this way, we end up multiplying 450 with 0.58 and 700 with 0.42. Why then am i ending up in the reverse order ? (the formula is given in the NCERT textbook-in terms of 1 and 2 instead of A and B)
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