Study Tips
A week before the examination
=> Look back at your revision programme. Is it complete? Aren’t there some things you want to look at again? Use this week for some focused revision.
=> Review your revision notes every day. Try reviewing your notes without looking at them. Which parts are difficult to remember? Concentrate on learning those parts.
=> Remember that the examination asks you to do things in English. It is not a test of how well you remember your notes. Use your time to do some relaxing things in English.
=> Look back at the written work you did a year ago. Do you see how much you have improved? Think positively about yourself and your achievements.
=> Think about what you are going to wear for the examination. You should be comfortable, but try to choose something special for this special day. This means that when you put on those clothes, you will already be preparing yourself for the examination.
=> Get as much sleep as you can. Don’t waste time worrying about the examination. You will not learn anything by worrying. Find some time to take exercise. You can try to remember phrasal verbs when you are jogging or plan a composition whilst you take a walk.
=> Travel to the place where you will take the examination. Check that you know the way and the time. Use the journey time to plan your examination strategy.
=> Remember to send ‘good luck’ messages to all your friends who are taking the same examination.
=> The night before the examination don’t eat a heavy meal. Eat something light but nutritious. Avoid alcohol. Take some exercise and go to bed early.
On the day of the examination
=> Dress in your ‘examination clothes’ and prepare yourself for this special day. Open and read the ‘good luck’ messages from your friends. Have a good breakfast but don’t drink too much. You shouldn’t feel hungry or uncomfortable in any way during the examination.
=> Check through the ‘time plan’ you have made for the examination. Know how much time you will give to each question. Check you have given yourself time for checking and correcting.
=> Check that you have all the pens and papers you need for the examination. For many examinations you may need some identification papers.
=> As you travel to the place of the examination, remind yourself of your examination strategy.
During the examination
=> Focus your mind on what you have to do. Don’t be distracted by outside things or by other students.
=> Keep an eye on the clock but try not to hurry. Always give yourself time to check your work.
=> Remember you will get no marks for any questions you do not attempt so make sure that you complete as much of the examination as possible.
After the examination
=> Don’t worry about the mistakes you made and the things you got wrong. You will have a long wait for the results so go out and enjoy your freedom!
=> The results are not as good as you expected? Well, you can always take the examination again. You are now a better, more organised person and a better learner. It will be much easier next time.
=> The results are good? Congratulations!
Showing posts with label Examinations. Show all posts
Showing posts with label Examinations. Show all posts
Sunday, March 23, 2008
Chemistry Examination Tips for CBSE Exam. Class X and XII
CHEMISTRY EXAM TIPS
Before the Exam
· Show up early. Walking in late might mean getting an uncomfortable seat, and most probably less time to take the exam.
· Freeways and traffic are a part of Los Angeles life...plan for it! Give yourself PLENTY of extra time to make the commute on exam days. Better to have a half hour extra to spend on campus than to arrive a half hour late for the exam.
· Bring an extra pen or pencil, eraser, and mechanical pencil leads.
· Do not bring pagers, cellular phones, Walkmen, portable CD players, etc., to the exam. They are not needed, and can disturb students around you. If you answer a cell phone or look at a pager during an exam, it will be assumed you are using it to cheat.
· Molecular models are allowed on all Hardinger exams. Calculators are forbidden on all Hardinger exams.
During the Exam
Perhaps the most important piece of advice is:
Think before you write!
Much precious time can be saved by spending a few seconds contemplating your answer before you spend the time to write it out. Your brain generally works much faster than your pen or pencil.
Some other advice:
· Examine all the problems first before you begin any of them. Do the problems you know first, saving the problems that will require more work for later. You have a limited period of time in which to earn your points, so do first the problems on which you will get the most points.
· Avoid suspicious behavior during the exam. Don't stare at other exams, fidget with your eraser, etc.
· A grader will assume you know material covered in a previous course or exam, but not a concept covered by the current exam.
· Never leave a question blank, unless you are told guessing will result in lost points.
· Always read instructions very, very, very carefully. Make sure you know what the question is asking.
· Make sure that your answer is in the format that the question asks for. For example, if the questions says "circle and label," then circle AND label. When in doubt, ask a TA, or better yet, the person who wrote the exam.
· If you don't quite understand what a question is asking, ask a TA or better yet the person who wrote the exam. You shouldn't lose points because the question is poorly worded. However, never bother to ask "is this right?" during an exam. The answer will be "I cannot tell you," and you have wasted your valuable exam time.
· Draw structures neatly. Communicating your thoughts with structural drawings is critical in chemistry. Sloppy drawings imply sloppy thinking.
· Write neatly. If your words cannot be understood, you will not get credit for them. If your name cannot be read, your exam score cannot be recorded, so you get no credit for it!
· Erase a wrong answer instead of scribbling it out. This leaves you with more space to write your corrected answer. Use a pen with easily erasable ink if you use a pen at all.
· Avoid non sequitar answers. That is, avoid adding details which don't answer the question directly. The time spent writing the non sequitar could be used for other answers. In addition, if the non sequitar information is wrong, you may lose points for it, whether or not it's relevant to the question.
· Avoid pentavalent carbons (carbons with 5 full bonds). Hexavalent carbons are even worse.
· If you make any assumptions about a question, write them down and clearly label them. Example: "I assumed the following for question 3...." If your assumption is reasonable for a student with an equivalent level of experience, your exam answer will be graded with this assumption in mind.
· If you continue an answer on the back of the page, include a clear notation such as "answer to this question continued on back of previous page." It is not the job of the graders to hunt for your answers.
· Spell chemical words correctly. Although this is not an English course, part of learning an subject is a mastery of it's vocabulary. In addition, be careful with your choice of words. Chemistry vocabulary is large because there are so many words that have very specific meanings. Perhaps the most common mistake is the use of "molecule" to refer to a fraction of a molecule, or a group of atoms which do not make up a whole molecule. Refer to such a fraction as "molecular fragment" or "group" or something like that.
· Make sure you use the right kinds of arrows!
· Consider the fact that your exam answers must stand for themselves. Use clear sentences! You cannot explain your answer after the exam and expect to regain any lost points.
· Quit when time is called, regardless of what you are writing or thinking. Continuing to write after the exam time is over is cheating, and there are penalties for cheating.
How to Handle Briefly Explain Questions
Briefly explain questions are designed to probe your knowledge of fundamental concepts, and your ability to articulate scientific ideas. Here are some thoughts about how to approach these questions, from the minds of the TAs and Dr Hardinger.
· "Briefly explain" also means ""outline" or "concisely discuss." Complete sentences are not necessary, as long as your logic is clear to the grader.
· Think before your write! A few seconds spent considering the answer before you put pen to paper might save you lots of time erasing and rewriting.
· Think about all the key concepts for a question before you begin to write your answer. Expect to explain any concepts that are new between this exam and the last. For example, on the second midterm, topics covered on the first midterm do not need to be explained, but topics presented in lecture since the first midterm do require explanation. A final is cumulative, so you should explain all new concepts for the course.
· Outline the answer first, if necessary. (You do this for a ten page paper, so why not for a briefly explain question as well?) A list of key words or phrases works well for this. You may find that your outline is a complete answer by itself. Avoid "stream of consciousness" writing.
· Organize and articulate your answer in a manner that your fellow classmates could understand. Pretend you are explaining the concept to someone who is in the class, but has not yet studied this exam material or attended lecture.
· Use precise and accurate wording when answering "briefly explain" questions. Consider the difference in these symptoms as explained by a patient: "I have a pain in my head" versus "I have an intermittent but dull throbbing pain that is occurring behind and above my left eye. The pain started yesterday around noon when I was hit in the left temple by a softball."
· Pack as much information into the answer as possible, but avoid irrelevant information. (Vast quantities of irrelevant information are sometimes called "intellectual vomit," and we all know how unpleasant that can be.) Scores tend to be proportional not to the number of facts, but rather to the concentration of relevant concepts in the answer. The number and accuracy of relevant concepts is more important than the number of words.
· Briefly explain questions are graded both on use of appropriate vocabulary and concepts. Just because you have not used the exact words on the key does not mean you cannot get full credit. However, certain words and phrases are very important and should be used. Experience with the course material is the best guide to what is and is not important. Graders are favorably impressed by the correct use of relevant vocabulary words.
· Avoid limiting statements such as "The only way..." These often lead to false generalizations with subsequent deduction of points.
· Eschew obfuscation. Elide cerebral entropism. (Just like these statements. Look it up!)
· Briefly explain answers in CFQs, Practice Problems and old exam keys are generally much longer than is expected on an exam. This is because these answers are also meant to provide a detailed archive for future students to learn the concepts of the question.
· The best briefly explain answers will show that you understand the concepts and can manipulate them intelligently, and that you have not just wasted your time memorizing the CFQs.
· The exam space provided for an answer is always adequate. If a small space is provided, that indicates that a shorter answer is sufficient. It should not be assumed, however, that large spaces mean long answers are required.
· Write and draw neatly. Points cannot be awarded for what cannot be interpreted
· Practice with writing briefly explain answers should be a routine study habit. If you find a good writing style, emulate it.
When You've Completed the Exam
· Check your answers if you have time. If your gut instinct is to leave an answer alone, then do so. Personal experience suggests that the "second guess" is often wrong if you have been studying correctly.
· Always collect your graded exam, and compare it with the key. (Exam keys are usually posted on the course web site within an hour of the exam's completion.) You can learn a lot by comparing your answers with those on the key.
Learning From Your Mistakes
· Once the exam is returned, carefully review your answers and try to understand why full credit was not earned. Consider this quote (allegedly from Karl Popper, an educational philosopher):
"The difference between the amoeba and Einstein is that, although both make use of the methods of trial and error or elimination, the amoeba dislikes erring while Einstein is intrigued by it. He consciously searches for his errors in the hope of learning by his discovery and elimination." Are you an amoeba or an Einstein?
· You may find it useful to print out a blank copy of the exam, and re-take it. This will give you more practice and help you become more familiar with the concepts.
Before the Exam
· Show up early. Walking in late might mean getting an uncomfortable seat, and most probably less time to take the exam.
· Freeways and traffic are a part of Los Angeles life...plan for it! Give yourself PLENTY of extra time to make the commute on exam days. Better to have a half hour extra to spend on campus than to arrive a half hour late for the exam.
· Bring an extra pen or pencil, eraser, and mechanical pencil leads.
· Do not bring pagers, cellular phones, Walkmen, portable CD players, etc., to the exam. They are not needed, and can disturb students around you. If you answer a cell phone or look at a pager during an exam, it will be assumed you are using it to cheat.
· Molecular models are allowed on all Hardinger exams. Calculators are forbidden on all Hardinger exams.
During the Exam
Perhaps the most important piece of advice is:
Think before you write!
Much precious time can be saved by spending a few seconds contemplating your answer before you spend the time to write it out. Your brain generally works much faster than your pen or pencil.
Some other advice:
· Examine all the problems first before you begin any of them. Do the problems you know first, saving the problems that will require more work for later. You have a limited period of time in which to earn your points, so do first the problems on which you will get the most points.
· Avoid suspicious behavior during the exam. Don't stare at other exams, fidget with your eraser, etc.
· A grader will assume you know material covered in a previous course or exam, but not a concept covered by the current exam.
· Never leave a question blank, unless you are told guessing will result in lost points.
· Always read instructions very, very, very carefully. Make sure you know what the question is asking.
· Make sure that your answer is in the format that the question asks for. For example, if the questions says "circle and label," then circle AND label. When in doubt, ask a TA, or better yet, the person who wrote the exam.
· If you don't quite understand what a question is asking, ask a TA or better yet the person who wrote the exam. You shouldn't lose points because the question is poorly worded. However, never bother to ask "is this right?" during an exam. The answer will be "I cannot tell you," and you have wasted your valuable exam time.
· Draw structures neatly. Communicating your thoughts with structural drawings is critical in chemistry. Sloppy drawings imply sloppy thinking.
· Write neatly. If your words cannot be understood, you will not get credit for them. If your name cannot be read, your exam score cannot be recorded, so you get no credit for it!
· Erase a wrong answer instead of scribbling it out. This leaves you with more space to write your corrected answer. Use a pen with easily erasable ink if you use a pen at all.
· Avoid non sequitar answers. That is, avoid adding details which don't answer the question directly. The time spent writing the non sequitar could be used for other answers. In addition, if the non sequitar information is wrong, you may lose points for it, whether or not it's relevant to the question.
· Avoid pentavalent carbons (carbons with 5 full bonds). Hexavalent carbons are even worse.
· If you make any assumptions about a question, write them down and clearly label them. Example: "I assumed the following for question 3...." If your assumption is reasonable for a student with an equivalent level of experience, your exam answer will be graded with this assumption in mind.
· If you continue an answer on the back of the page, include a clear notation such as "answer to this question continued on back of previous page." It is not the job of the graders to hunt for your answers.
· Spell chemical words correctly. Although this is not an English course, part of learning an subject is a mastery of it's vocabulary. In addition, be careful with your choice of words. Chemistry vocabulary is large because there are so many words that have very specific meanings. Perhaps the most common mistake is the use of "molecule" to refer to a fraction of a molecule, or a group of atoms which do not make up a whole molecule. Refer to such a fraction as "molecular fragment" or "group" or something like that.
· Make sure you use the right kinds of arrows!
· Consider the fact that your exam answers must stand for themselves. Use clear sentences! You cannot explain your answer after the exam and expect to regain any lost points.
· Quit when time is called, regardless of what you are writing or thinking. Continuing to write after the exam time is over is cheating, and there are penalties for cheating.
How to Handle Briefly Explain Questions
Briefly explain questions are designed to probe your knowledge of fundamental concepts, and your ability to articulate scientific ideas. Here are some thoughts about how to approach these questions, from the minds of the TAs and Dr Hardinger.
· "Briefly explain" also means ""outline" or "concisely discuss." Complete sentences are not necessary, as long as your logic is clear to the grader.
· Think before your write! A few seconds spent considering the answer before you put pen to paper might save you lots of time erasing and rewriting.
· Think about all the key concepts for a question before you begin to write your answer. Expect to explain any concepts that are new between this exam and the last. For example, on the second midterm, topics covered on the first midterm do not need to be explained, but topics presented in lecture since the first midterm do require explanation. A final is cumulative, so you should explain all new concepts for the course.
· Outline the answer first, if necessary. (You do this for a ten page paper, so why not for a briefly explain question as well?) A list of key words or phrases works well for this. You may find that your outline is a complete answer by itself. Avoid "stream of consciousness" writing.
· Organize and articulate your answer in a manner that your fellow classmates could understand. Pretend you are explaining the concept to someone who is in the class, but has not yet studied this exam material or attended lecture.
· Use precise and accurate wording when answering "briefly explain" questions. Consider the difference in these symptoms as explained by a patient: "I have a pain in my head" versus "I have an intermittent but dull throbbing pain that is occurring behind and above my left eye. The pain started yesterday around noon when I was hit in the left temple by a softball."
· Pack as much information into the answer as possible, but avoid irrelevant information. (Vast quantities of irrelevant information are sometimes called "intellectual vomit," and we all know how unpleasant that can be.) Scores tend to be proportional not to the number of facts, but rather to the concentration of relevant concepts in the answer. The number and accuracy of relevant concepts is more important than the number of words.
· Briefly explain questions are graded both on use of appropriate vocabulary and concepts. Just because you have not used the exact words on the key does not mean you cannot get full credit. However, certain words and phrases are very important and should be used. Experience with the course material is the best guide to what is and is not important. Graders are favorably impressed by the correct use of relevant vocabulary words.
· Avoid limiting statements such as "The only way..." These often lead to false generalizations with subsequent deduction of points.
· Eschew obfuscation. Elide cerebral entropism. (Just like these statements. Look it up!)
· Briefly explain answers in CFQs, Practice Problems and old exam keys are generally much longer than is expected on an exam. This is because these answers are also meant to provide a detailed archive for future students to learn the concepts of the question.
· The best briefly explain answers will show that you understand the concepts and can manipulate them intelligently, and that you have not just wasted your time memorizing the CFQs.
· The exam space provided for an answer is always adequate. If a small space is provided, that indicates that a shorter answer is sufficient. It should not be assumed, however, that large spaces mean long answers are required.
· Write and draw neatly. Points cannot be awarded for what cannot be interpreted
· Practice with writing briefly explain answers should be a routine study habit. If you find a good writing style, emulate it.
When You've Completed the Exam
· Check your answers if you have time. If your gut instinct is to leave an answer alone, then do so. Personal experience suggests that the "second guess" is often wrong if you have been studying correctly.
· Always collect your graded exam, and compare it with the key. (Exam keys are usually posted on the course web site within an hour of the exam's completion.) You can learn a lot by comparing your answers with those on the key.
Learning From Your Mistakes
· Once the exam is returned, carefully review your answers and try to understand why full credit was not earned. Consider this quote (allegedly from Karl Popper, an educational philosopher):
"The difference between the amoeba and Einstein is that, although both make use of the methods of trial and error or elimination, the amoeba dislikes erring while Einstein is intrigued by it. He consciously searches for his errors in the hope of learning by his discovery and elimination." Are you an amoeba or an Einstein?
· You may find it useful to print out a blank copy of the exam, and re-take it. This will give you more practice and help you become more familiar with the concepts.
Chemistry Sample CBSE Examination Paper Class XII
SAMPLE QUESTION PAPER - I
CHEMISTRY
CLASS XII
Time Allowed : 3 Hours Maximum Marks : 70
GENERAL INSTRUCTIONS
All questions are compulsory.
Marks for each question are indicated against it.
Question numbers 1 to 5 are very short answer question, each of 1 mark. Answer these in one world or about one sentence each.
Question numbers 6 to 12 are short answer questions of 2 marks each of one mark. Answer these in about 30 words each.
Questions number 13 to 24 are short answer questions of 3 marks each. Answer these in about 40 words each.
Question numbers 25 to 27 are long answer questions of 5 marks each. Answer these in about 70 words each.
Use log tables if necessary. Calculators are not permitted.
How many effective sodium ions are located at the centres of faces of a unit cell in a sodium chloride crystal?
A reaction:
Reactant > product is represented by
Predict
The order of the reaction in this case
What does the slope of the following reaction
Propose the mechanism for the following reaction:
Write the IUPAC name of the compound.
Carefully examine the diagram and name the process involved:
Identify the type of inter molecular forces that exist between the following pairs:
(i) Na+ ion and water molecules
(ii) Ag+ ion and I- ion
(iii) Argon and Argon
(iv) HF and H2O
Predict the entrophy change (Positive/Negative) in the following:
(i) A liquid substance crystallizes into a solid
(ii) Temperature of crystal is increased.
(iii) CaCO3(s) > CaO(s) + CO2(g)
(iv) N2 (1 atm) (g) > N2 (0.5 atm) (g)
How is [(CH3)2 SiO]n prepared? Write its two applications.
What is a stereospecific reaction? Give one example of this reaction.
Identify A, B, C, and D in the following reactions.
OR
Write the reactions and conditions involved in the following conversions?
Acetic acid into ethy alcohol
Cumene into phenol
The presence of benzoquinone inhibits the free radical polymerization of a Vinyl derivative”. Explain.
What are anomers? How many anomers of glucose are known? Name them.
(a) Calculate the energy of photon which is necessary to raise an electron in hydrogen atom from n=1 to n=3 energy level? (Given the ionization energy of hydrogen atom is 1.312 ×103 kJ mol-1and NA=6.02 × 1023 mol-1).
(b) Which of the following excitations required maximum energy?
n1 >n2
n2 >n3
n3 >n4
or all require the same energy.
OR
Suppose the velocities of an electron and a rifle bullet of mass 0.03 kg are each measured with an uncertainity of v =10-3 m s-1 calculate the minimum uncertainities in their positions. (Given: mass of an electron =9,1 x 10-31 kg)
Comment on the calculated values of uncertainities in positions in the two cases.
Explain the following terms with suitable examples:
Ferrimagnetism
n-type semiconductor
forbidden zone
The Henry law constant for oxygen dissolved in water is 4.34 × 104 atm at 250C. If the partial pressure of oxygen in air is 0.2 atm. Under ordinary atmospheric conditions. Calculate the concentration (in moles per litre) of dissolved oxygen in water in equilibrium with air at 250C.
At elevated temperatures, HI decomposes according to the chemical equation:
2HI (g) >H2 (g) + I2 (g)
at 4430C. The rate of the reaction increases with concentration of HI, as shown in the following table:
1 2 3
HI (mol L-1)
Rate (mol L-1 s-1) 0.005
7.5 × 10-4
0.01
3.0 × 10-3
0.02
1.2 × 10-2
(a) Determine (i) order of this reaction and (ii) write the rate expression.
(b) Calculate the rate constant and give its units.
(a) Among the iron complexes, K3 [Fe(CN)6] shows very low parqamagnetism where as K3[FeF6] is highly paramagnetic explain.
(b) Define crystal field orbital splitting energy.
( c ) Write the shape of Fe(CO)5 molecule.
Represent the following using a nuclear equation of each:
Production of C-14 in nature
b-emission
K-capture
Write chemical tests to distinguish the following pair of compounds:
(b) Write a chemical equation examplifying Clemmensen reduction.
Give reasons of the following:
(a)
The basic strength of aliphatic amines in solution is in the order sec.> tert. > primary.
Nitro compounds have higher boiling than hydrocarbons having nearly same molecular mass.
(b) By giving an example describe carbylamine reaction.
(a) Which bonds in the back bone of a peptide can rotate freely and which cannot? Give reasons.
(b) Write one difference between parallel and antiparallel b pleated sheets. Give one example of parallel pleated sheet.
Answer the following :
(a) An unknown fibre (A) is stronger than steel, stiffer than titanium an lighter than aluminium.
What could the fibre (A) be?
(b) Why are liquid propellants favoured over solid propellants?
(c) What type of medicines are omeprazole and Lansoprazole?
The change in entropy with respect to temperature in case of a sample is graphically represented below:
Carefully analyse the graph and answer the following:
(i) What does T1 and T2 indicate?
(ii) What does AB curve show?
(iii) What does BC curve show? Why temperature does not change?
Describe the following giving one example each:
(a) Mechanism of heterogeneous catalysis.
(b) Hardy Schulze Rule
(a) Write the reactions occurring during the electrodes of.
Sulphuric acid at the anode
Aqueous Silver nitrate solution using silver electrodes.
Aqueous sodium chloride solution.
(b)
Write the anodic and cathodic reactions involved during the discharging of lead storage battery.
How many Faraday’s of electric charge is involved per mole of H2SO4 consumed, when the lead storage battery is in use?
OR
(a) In the Leclanche cell write the following:
The chemical equations involved at the cathode.
Change in the Oxidation state of Mn.
The complex entity formed between Zn2+ (aq) and NH3 (g).
(b) In a hydrogen - oxygen fuel cell write the reactions involved at the anode and the cathode.
(c) How will the value of Ecell change in an electrochemical cell involving the following reaction if the concentration of Ag+ (aq) is increased?
Mg(s) + 2Ag+ (aq) > Mg2+ (aq)+ Ag (s)
(d) Why is mercury cell used in hearing aids?
(a) Identify the species from A to D in the extraction of silver from its ore (A)
(b) Give reasons for the following:
With d4 configuration Cr2+ is reducing where as Mn3+ is oxidizing.
Interstitial compounds are well known for transition metals.
The highest oxidation state of a metal is exhibited is exhibited in oxides and fluorides.
Account for the following:
All the bonds in PCI5 are not equivalent
Sulphur in vapour state exhibits paramagnetism
Fluorine is the strongest oxidant amongst the halogens.
Among the noble gases, only xenon is known to form true chemical compounds.
PbO2 is a stronger oxidizing agent than SnO2.
CHEMISTRY
CLASS XII
Time Allowed : 3 Hours Maximum Marks : 70
GENERAL INSTRUCTIONS
All questions are compulsory.
Marks for each question are indicated against it.
Question numbers 1 to 5 are very short answer question, each of 1 mark. Answer these in one world or about one sentence each.
Question numbers 6 to 12 are short answer questions of 2 marks each of one mark. Answer these in about 30 words each.
Questions number 13 to 24 are short answer questions of 3 marks each. Answer these in about 40 words each.
Question numbers 25 to 27 are long answer questions of 5 marks each. Answer these in about 70 words each.
Use log tables if necessary. Calculators are not permitted.
How many effective sodium ions are located at the centres of faces of a unit cell in a sodium chloride crystal?
A reaction:
Reactant > product is represented by
Predict
The order of the reaction in this case
What does the slope of the following reaction
Propose the mechanism for the following reaction:
Write the IUPAC name of the compound.
Carefully examine the diagram and name the process involved:
Identify the type of inter molecular forces that exist between the following pairs:
(i) Na+ ion and water molecules
(ii) Ag+ ion and I- ion
(iii) Argon and Argon
(iv) HF and H2O
Predict the entrophy change (Positive/Negative) in the following:
(i) A liquid substance crystallizes into a solid
(ii) Temperature of crystal is increased.
(iii) CaCO3(s) > CaO(s) + CO2(g)
(iv) N2 (1 atm) (g) > N2 (0.5 atm) (g)
How is [(CH3)2 SiO]n prepared? Write its two applications.
What is a stereospecific reaction? Give one example of this reaction.
Identify A, B, C, and D in the following reactions.
OR
Write the reactions and conditions involved in the following conversions?
Acetic acid into ethy alcohol
Cumene into phenol
The presence of benzoquinone inhibits the free radical polymerization of a Vinyl derivative”. Explain.
What are anomers? How many anomers of glucose are known? Name them.
(a) Calculate the energy of photon which is necessary to raise an electron in hydrogen atom from n=1 to n=3 energy level? (Given the ionization energy of hydrogen atom is 1.312 ×103 kJ mol-1and NA=6.02 × 1023 mol-1).
(b) Which of the following excitations required maximum energy?
n1 >n2
n2 >n3
n3 >n4
or all require the same energy.
OR
Suppose the velocities of an electron and a rifle bullet of mass 0.03 kg are each measured with an uncertainity of v =10-3 m s-1 calculate the minimum uncertainities in their positions. (Given: mass of an electron =9,1 x 10-31 kg)
Comment on the calculated values of uncertainities in positions in the two cases.
Explain the following terms with suitable examples:
Ferrimagnetism
n-type semiconductor
forbidden zone
The Henry law constant for oxygen dissolved in water is 4.34 × 104 atm at 250C. If the partial pressure of oxygen in air is 0.2 atm. Under ordinary atmospheric conditions. Calculate the concentration (in moles per litre) of dissolved oxygen in water in equilibrium with air at 250C.
At elevated temperatures, HI decomposes according to the chemical equation:
2HI (g) >H2 (g) + I2 (g)
at 4430C. The rate of the reaction increases with concentration of HI, as shown in the following table:
1 2 3
HI (mol L-1)
Rate (mol L-1 s-1) 0.005
7.5 × 10-4
0.01
3.0 × 10-3
0.02
1.2 × 10-2
(a) Determine (i) order of this reaction and (ii) write the rate expression.
(b) Calculate the rate constant and give its units.
(a) Among the iron complexes, K3 [Fe(CN)6] shows very low parqamagnetism where as K3[FeF6] is highly paramagnetic explain.
(b) Define crystal field orbital splitting energy.
( c ) Write the shape of Fe(CO)5 molecule.
Represent the following using a nuclear equation of each:
Production of C-14 in nature
b-emission
K-capture
Write chemical tests to distinguish the following pair of compounds:
(b) Write a chemical equation examplifying Clemmensen reduction.
Give reasons of the following:
(a)
The basic strength of aliphatic amines in solution is in the order sec.> tert. > primary.
Nitro compounds have higher boiling than hydrocarbons having nearly same molecular mass.
(b) By giving an example describe carbylamine reaction.
(a) Which bonds in the back bone of a peptide can rotate freely and which cannot? Give reasons.
(b) Write one difference between parallel and antiparallel b pleated sheets. Give one example of parallel pleated sheet.
Answer the following :
(a) An unknown fibre (A) is stronger than steel, stiffer than titanium an lighter than aluminium.
What could the fibre (A) be?
(b) Why are liquid propellants favoured over solid propellants?
(c) What type of medicines are omeprazole and Lansoprazole?
The change in entropy with respect to temperature in case of a sample is graphically represented below:
Carefully analyse the graph and answer the following:
(i) What does T1 and T2 indicate?
(ii) What does AB curve show?
(iii) What does BC curve show? Why temperature does not change?
Describe the following giving one example each:
(a) Mechanism of heterogeneous catalysis.
(b) Hardy Schulze Rule
(a) Write the reactions occurring during the electrodes of.
Sulphuric acid at the anode
Aqueous Silver nitrate solution using silver electrodes.
Aqueous sodium chloride solution.
(b)
Write the anodic and cathodic reactions involved during the discharging of lead storage battery.
How many Faraday’s of electric charge is involved per mole of H2SO4 consumed, when the lead storage battery is in use?
OR
(a) In the Leclanche cell write the following:
The chemical equations involved at the cathode.
Change in the Oxidation state of Mn.
The complex entity formed between Zn2+ (aq) and NH3 (g).
(b) In a hydrogen - oxygen fuel cell write the reactions involved at the anode and the cathode.
(c) How will the value of Ecell change in an electrochemical cell involving the following reaction if the concentration of Ag+ (aq) is increased?
Mg(s) + 2Ag+ (aq) > Mg2+ (aq)+ Ag (s)
(d) Why is mercury cell used in hearing aids?
(a) Identify the species from A to D in the extraction of silver from its ore (A)
(b) Give reasons for the following:
With d4 configuration Cr2+ is reducing where as Mn3+ is oxidizing.
Interstitial compounds are well known for transition metals.
The highest oxidation state of a metal is exhibited is exhibited in oxides and fluorides.
Account for the following:
All the bonds in PCI5 are not equivalent
Sulphur in vapour state exhibits paramagnetism
Fluorine is the strongest oxidant amongst the halogens.
Among the noble gases, only xenon is known to form true chemical compounds.
PbO2 is a stronger oxidizing agent than SnO2.
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