JEE has been divided into two exams: JEE Main and JEE Advanced. JEE Main 2018 is the preliminary stage of JEE, which is scheduled to be held on April 8, 2018 in offline mode and JEE Main 2018 computer based test will be conducted on April 15 and 16, 2018. Those who will qualify JEE Main 2018 will be eligible to appear for JEE Advanced. Students who qualify both exams will be short listed for admissions to engineering courses at IITs, NITs, and CFTIs.
Above is the very brief information about the JEE Main and JEE advanced. Once the candidates have submitted the application forms, it becomes very challenging to make a right study plan to crack these exams.
Most of the aspirants preparing for JEE Main and JEE Advanced are fresh candidates which means they are going to appear in the exam right after their board exams.
The other category is of repeaters who are going to take the JEE Main test for the second time to improve their rank. Such candidates would have been preparing for this entrance exam by taking various coaching classes or simply doing self-studies.
Let us discuss first about the JEE Main, the preliminary test which is scheduled to be held on April 8, 2018. The syllabus of the JEE Main exam is based on the class 11th and class 12th NCERT books which is a favorable factor for the fresher students. But repeaters can also take a lead by revising their whole year’s learning in a proper way.
All the aspirants need to keep a track of their preparedness by practicing more and more questions based on each important topic for JEE Main test.
Find the 5 most important questions from the topic Order of Reaction for the examination. Students always find about 1-2 questions from this topic in the examination.
Every day you will get the entirely FRESH 5 Questions for JEE Main.
7th Feb, 2018: 5 Important Questions of Order of Reaction for JEE Main 2018
Q1. Which of the following statements is not correct about order of a reaction?
Options:
(a) The order of a reaction can be a fractional number
(b) Order of a reaction is experimentally determined quantity
(c) The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction
(d) The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression
Ans. Option (c) is not correct
Explanation:
Order of reaction is equal to the sum of powers of concentration of the reactants in rate law expression.
For any chemical reaction
Order of reaction can be a fraction also. Order of reaction is not always equal to sum of the stoichiometric coefficients of reactants in the balanced chemical equation. For a reaction it may or may not be equal to sum of stoichiometric coefficient of reactants.
Q2. In a reaction if the concentration of reactant A is doubled, the rate of reaction becomes eight times. What is the order of the reaction?
Options:
(a) 2
(b) 3
(c) 8
(d) 4
Ans. Option (a) is correct
Explanation:
Q3. The expression to calculate time required for completion of zero order reaction is
Options:
Q 5. For a complex reaction …………
Options:
(a) molecularity of the slowest step can be zero or non-integer
(b) order of overall reaction is less than the molecularity of the slowest step
(c) order of overall reaction is greater than molecularity of the slowest step
(d) order of overall reaction is same as molecularity of the slowest step
Ans. Option (d) is correct
Explanation:
For a complex reaction, order of overall reaction = molecularity of slowest step
As rate of overall reaction depends upon total number of molecules involved in slowest step of the reaction. Hence, molecularity of the slowest step is equal to order of overall reaction.
6th Feb, 2018: 5 Important Questions of Gravitation for JEE Main 2018
Q1. Four particles, each of mass M and equidistant from each other, move along a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is:
Options:
5th Feb, 2018: 5 Important Questions of Limits for JEE Main 2018
2nd Feb, 2018: 5 Important Questions of Isomerism for JEE Main 2018
Q1. Find out the number of enantiomer, meso isomer and total number of optical isomers for the following compound
Options:
(a) 3,2,4
(b) 0,2,3
(c) 4,0,4
(d) 0,2,2
Ans. Option (c) is correct
Explanation: before solving the or guessing the options, you should check either the given molecule is symmetrical or unsymmetrical
The given molecule is unsymmetrical as it has group X at one end and group Y at other end
Then after you need to find out the number of chiral carbon
So, the number of chiral carbon in the given compound is: 2
Now come to formula to calculate the number of enantiomer, meso isomer and total number of optical isomers
1. Number of enantiomer = 2n (n is the number of chiral carbon )
2. Number of meso isomer = ZERO
Note:
A meso compound is one which is optically inactive although have more than one chiral carbons.
3. Total number of optical isomer= 2n + 0
So in the above question,
Chiral carbon, n= 2
So Number of enantiomer = 2n = 22 = 4
Number of meso isomer = ZERO
Total number of optical isomer= 2n + 0 = 4+0= 4
Q 2. The number of enantiomer in a glucose molecule is
Options:
(a) 16
(b) 12
(c) 4
(d) 9
Ans. Option (a) is correct
Explanation: first you should look at the glucose structure
And the find out the number of chiral carbon which will be denoted by n
Here in Glucose molecule the number of chiral carbon is = 4, as shown in the figure
As we have seen the formula above to calculate the number of enantiomer, = 2n
So, total number of enantiomer in Glucose molecule is: 24 = 16
Note:
• The combination of d(+) and l(-) isomer is known as enantiomer
• Enantiomer reacts with different speed with different chiral reagent
• The stereoisomers which are non superimposable mirror images of each other is known as enantiomer
Q 3. Enantiomer can be separated by use of
Options:
(a) Enzymes
(b) Physical method
(c) Chemisorption
(d) Rotation
Ans. Option (a) is correct
Explanation: Enantiomer has different biological properties and hence can be separated by enzymes
Q4. Select the correct stability order of the conformation /Rotamers/ Rotational isomers of Ethane Molecule
Options:
(a) Partially Eclipsed > Fully Eclipsed > Anti-staggered > Skew or Gouche
(b) Skew or Gouche > Partially Eclipsed > Fully Eclipsed > Anti-staggered
(c) Anti-staggered > Skew or Gouche > Partially Eclipsed > Fully Eclipsed
(d) Fully Eclipsed > Anti-staggered > Skew or Gouche > Partially Eclipsed >
Ans. Option (c) is correct
Explanation:
• The isomers which can be produced by the free rotation about single bond are known as conformation /Rotamers/ Rotational isomers and this phenomenon is called as conformational analysis
• These isomers can be represented by
1. sawhorse projection
2. Newman’s projection formula
3. A staggered conformer is more stable than an eclipsed conformer as the latter involves unfavourable energy interactions between atoms.
4. In conformational analysis (energetics study of different rotational conformers or rotamers), structures are represented by *Newman projection * (atoms and bonds are viewed along the axis of rotation).
Q5. Beckmann rearrangement is not catalysed by
Options:
(a) H2SO4
(b) P2O5
(c) BF3
(d) NaOH
Ans. Option (d) is correct
Explanation: Beckmann rearrangement is only catalysed by Acid catalyst and used to determined the configuration of ketoximes
Above questions, answers and solutions are 100% unique and easy to understand.
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