Let’s Revise “Solid State” and “Solutions”

Friends, with just a few days left before the examination, you all must be busy completing the final round of revision. We often get queries from our students that they are finding it hard to cope up with the physical chemistry portion. This makes many of them, skip numericals especially related to solutions and electrochemistry. But you know what, this is the most scoring portion too. You have only five chapters with some laws, postulates, graphs and numericals.

Here, we will focuss on the important points of the first two chapters. Also after both the chapters we will have a glance of the previous years’ board question.

Let’s proceed….

Unit 1: Solid state (4 marks)

• Do read the definitions given in the NCERT book for the terms Pseudo solids or Super cooled liquids, isotropic and anisotropic solids, molecular solids, Bravais lattice.
• For predicting formulae of compounds you need to revise the total number of atoms  per unit cell For simple cubic unit cell it is 1, For bcc it is 2 and for fcc it is 4.
• Number of octahedral voids = Number of atoms  and Number of tetrahedral voids = Twice the number of atoms
• For unit cell dimension the important formula is M= dN_aa³/ z
• Imperfections in solids-

• Classification of solids based upon conductivities: Conductors, insulators and semi-conductors
• Classification of solids based upon magnetic properties: Paramagnetic, diamagnetic, ferromagnetic, anti-ferromagnetic and ferrimagnetic

Questions asked in previous years

Unit 2: Solutions 5 marks

• Raoult’s law: For a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction. p₁ = x₁p₁°
• Dalton’s law of partial pressure: The total pressure over the solution phase in the container is the sum of the partial pressures of the components of the solution. p_total = p1 + p2
• Henry’s law: Mole fraction of a gas in solution is proportional to the partial pressure of the gas over the solution. p = K_hx

Formulae for numericals

Mass % = (Mass of component in solution/ Total mass of the solution) * 100

Volume % = (Volume of component in solution/ Total volume of the solution) * 100

ppm =(No. of parts of the component/ Total no. of parts of all components of solution) * 100

Mole fraction = No. of moles of component/ Total no. of moles of all components

Molarity = (Moles of solute/ volume of solution in litres)

Molality = Moles of solute/ Mass of solvent in kg

Relative Lowering of vapour pressure

Elevation of boiling point

Depression of freezing point

Osmosis and Osmotic Pressure

van’t Hoff Factor

Important graphs

asdafs

So, just go through all the important points. For numericals prefer using logarithmic tables. Do not go for calculation in each and every question. Do the calculation part in the last step. If you stick to this practice, you will observe that most of the numeric values as well as units get cancelled out in the last step. This would ease the process at the same time will take much less time.

Best of luck

Team MeritNation

9 comments March 7th, 2012

Get solved CBSE board papers 2012 at Meritnation.com!

All you CBSE students appearing for class X & XII board exams can now log onto Meritnation.com after your exams to view detailed solutions for all questions in CBSE 2012 Board Papers. These solved board papers will be available at Meritnation.com in easily downloadable PDF format. Students can access solved board papers for CBSE Maths, Science, Physics, Chemistry, Biology, Economics, Accountancy, English, Hindi and Social Science at Meritnation.com absolutely free!

So what are you waiting for? Check-out the solved board papers at Meritnation.com and assess your performance in these board exams.

Cheers!
Team Meritnation

57 comments March 2nd, 2012

Cracking 2012 Chemistry Board Examination

Piles of notes, loads of books around, last minute revision and late night studies! Yes, Boards have reached your doorsteps. The last few days before the examination call for ‘smart and quick study’.

Reactions, reagents, laws and postulates are the lifeline of chemistry. If you are well prepared with these stuffs, then you should have no reason to worry about your performance.

Remember that,

As combination of elements make compounds,
similarly combination of efforts make success.

With the board examinations having just arrived at your doorsteps, here are few last minute preparation tips to help you excel in the subject.

How to Revise:–

• Don’t take stress.
• Realize your grey-areas in the subject.
• Do not study anything new before examination.
• Divide your time in accordance with the weightage of chapters.
• Start revising your notes and keep a glossary of important words.
• Be well-versed with the format of paper and marks allotted to each chapter.
• Practice CBSE sample papers and previous years’ board papers.
• Take at least one mock test on your own by randomly selecting a sample test paper. Stick to the exact duration of the test. Do not take break in between. Try to simulate the exam conditions as far as possible.
• Go through the NCERT solutions thoroughly. For this you can also refer to the NCERT solution section on meritnation.com.
• Physical chemistry: Revise the laws, postulates, formulae and graphs
• Inorganic chemistry: Revise the structures, oxidation states, chemical reactions and periodic trends.
• Organic chemistry: Revise name reactions, distinction tests and IUPAC nomenclature.
• Clear your doubts related to any topic immediately. You can always post your doubts on ‘Ask and Answer’ on meritnation.com and get expert help. Remember “Expert help is just a click away’.

During the Examination:–

• Read the question paper thoroughly in the initial 15 minutes.
• Mark the questions you are confident in answering.
• Write the correct question numbers for the answers.
• Do not leave sheets blank in between your answers.
• In the answer-sheet write the answers of all questions of one section at one place. Also, all the parts of a question need to be answered in sequence.
• Avoid leaving any answer blank. Try to write the closest answer you remember.
• Draw lines for rough work on the right hand side of the answer sheet. This would minimize the chances of errors in noting down the answer (especially the numeric values) from rough calculations done on some other page of the answer sheet.
• In the answer sheet, use black or blue coloured ink only.
• Underline the keywords in the answer.
• All equations must be balanced. A reaction, which is not balanced, is not an equation.

• Reasoning questions carry one mark each and demand to-the point and precise answer.

• Attempting numericals:

Start the answer by writing the skeleton formula in standard notation followed by substitution of values with units.
Numericals carry step-wise marking. At times it happens that due to lack of time these questions remain unattempted. In that case, even if you write the general formula and substitute the values, you manage to score half of the total marks alloted to the question.

Ques: A solution prepared by dissolving 1.25 g of oil of winter green (methyl salicylate) in 99.0 g of benzene has a boiling point of 80.31 °C. Determine the molar mass of this compound. (B.P. of pure benzene = 80.10 °C and Kb for benzene = 2.53 °C kg mol−1)    (CBSE 2010 Set 3, Q 21)

• Conversion of units should be taken care of. The final answer must be written with units.
• Always support your answers with structures, examples, equations and graphs even if the question does not ask for it.
• Memory-based questions are usually asked from the chapters like polymers, chemistry in everyday life, biomolecules and surface chemistry.

A little hard work with a little smartness will make you come out with flying colours in the upcoming chemistry examination. So focus on time management, topic-wise revision, self-assessment and then Chemistry will be a pleasant and successful experience for you!!!

All the Best

Shukla Paladhi
Team Meritnation

8 comments March 1st, 2012

Some Important tips for Mathematics exam

Hi friends!! Tensed?? Worried?? No need to worry for mathematics. Mathematics is not at all difficult. All you need is to revise everything and be careful while writing your answers. Here are some tips which will be really helpful for you to score full marks in Maths.

Tips to be followed during Maths exam:

1. In case you get stuck while solving any question, don’t panic. Leave appropriate space and don’t even cross out some of the steps that you may have written. This will ensure that even if you don’t find time to solve the question, the examiners will give some marks as step-wise marking system is followed in Maths exam.

2. Ensure that figures/tables should be on the same page as it saves your time in looking at the figure and finding the solution.

3. Always draw line for rough work on the right hand side of every page. This would minimize the chances of error in noting down the numeric values from rough calculations done on some other page of the answer sheet.

4. Using pencil make neat and clean figures. This would also enable you to change the figure in case need arises. Do not waste time in decorating the figure. A simple figure with perfect labelling will help you get full marks.

5. Write the steps of construction in all the questions involving constructions even if not asked in question.

6. Do not forget to write the statements of the theorems or results used in the solutions. Also, write each and every formula used in solution.
7. Do not forget to write the units in the questions involving dimensions.

General tips:

1. Proper planning is the key to success. Use the initial15 minutes smartly in scanning the entire question paper. Keep on tick marking the questions that you find at your grip. First attempt these questions then the rest.

2. Do not forget to write the section name before solving questions of any section.

3. Extra sheets should be tied in proper order.

4. Try to avoid crossing in answer sheet (specially on first page).

5. Remember to carry the required stationery items like scale, protractor,pencil, eraser etc with you.

6. Enough space (2 lines) should be left in between solutions of two different questions.

7. Your handwriting should be neat and easily readable.

8. Solve only one part of questions having two choices.

9. Manage your time in such a way that you can have enough time to revise your paper as it minimizes the chances of errors.
10. If you do not have any clue to solve some questions and some time is still left out, try to show your effort by writing at least the introductory steps and even etch out figures/diagrams/tables if relevant to the questions.

The way question is solved is most important. So, try to give a perfect answer.

Here is the screenshot of an answer sheet attempted by one of the Class X students who got full marks in mathematics. Look at the way the answer is presented in the answer sheet.

So, just focuss on the following points:

1. Figures with perfect labellings
2. No wastage of time in decoration
3. Step-by-step answering
4. No cutting in the answer sheet
5. Every single word and number must be readable

Click on the link to find out the most common errors that students make:- Math Common Errors in Maths Grade 10

Best of luck!!

9 comments February 29th, 2012

Physics Scoring Tips - Units 6, 7, 8

CBSE has given maximum weightage to the unit Optics with one long answer and some very short and short type answers. Units such as Dual Nature of Radiation and Matter,  Atoms and Nuclei are given low weightage but they are highly scoring if one remembers the formulae, definitions and graphs.

Unit 6: OPTICS (14 marks)

Want to secure a full-five marks score in optics?
A smart way of doing this is practising previous years’ questions and getting common questions. Here is a quick analysis of topics on which questions were asked repeatedly by CBSE in the five marks question pattern.

(You may go through the detailed solution of the board papers by clicking on the hyperlinks)

This analysis gives a clear idea of repetition of questions in board papers. Few topics which are very much essential for further study in physics will always be tested in the board exams.

More the number of previous papers solved, higher the chance of getting COMMON QUESTIONS. Click here for previous years’ board papers.

Unit 7: Dual Nature of Radiation and Matter (4 marks)

Q: An electron is accelerated through a potential difference of 64 volts. What is the de-Broglie wavelength associated with it? To which part of the electromagnetic spectrum does this value of wavelength correspond?   (CBSE 2010, 2 marks)

This question can be easily solved if you know the application of the formula:

Unit 8: Atoms and Nuclei (6 marks)

For mastering this unit you need to master the formulae. Make a list of all the important formulae in this unit with at least one application in numerical solving. Questions from this units are basically definitions, graphs and formula based numericals.

Q: The energy levels of an atom are as shown below. Which of them will result in the transition of a photon of wavelength 275 nm?Which transition corresponds to emission of radiation of maximum wavelength?     (CBSE 2009, 3 marks)

The formula E = hc/λ is sufficient to give you three marks in this question.

So, for this unit make sure you go through Rutherford’s model, Bohr’s model, Hydrogen spectra, Radioactive decays, Nuclear reactions (fission and fusion).

Follow these simple things and we are sure that you’ll manage to add the entire 24 marks from these units into your account.

To revise the formulae based on these units, click on the link: Formula Sheet ( Unit  6, 7, 8 )

Good Luck!
Team Meritnation

3 comments February 29th, 2012

GENERAL TIPS FOR PHYSICS (For Class XII)

Physics is not a literature subject. However, we study the concepts in literary format. But as far as physics is concerned, simply memorizing the notes will do no good. There are units, diagrams, formulas, numericals, concepts, mathematical forms that make this subject quite different from all other subjects.

Don’t panic; just be calm because when you have a will to score high, we are here to show you the way to do it.

Let’s start with the unit-wise distribution of marks as given by the CBSE board.

Unit-wise distribution of marks:

Following are some important points a student must follow to make good use of his knowledge on the subject and score a respectable score.

1. Make a chapter-wise list of all the concepts and the laws you have learned throughout the year.
2. Make a chapter-wise list of all the important SI units, formulae and constants you have learned throughout the year.
3. Always go for mathematical expressions and technical terms while answering the questions.
4. Wherever possible give labelled diagrams to reduce the number of words in your answers.
5. Whenever you draw a circuit, be careful with the direction of current and polarity of cells.
6. Follow standard books for derivations. Do not try to invent new ways for any derivation in the examination hall.
7. Always give step-wise solution to numericals because marks are allotted to each of the steps.
8. Be specific with your answers. Neither write too much nor too less.
9. Make your preparation syllabus-oriented. For last moment preparations, do not think about learning something out of syllabus or new concept.
10. Solve at least 5 previous years’ board papers without choice. This will help you evaluate where you stand and also give you some idea about what to expect.

All the Best!
Team Meritnation

4 comments February 29th, 2012

EXAM TIPS FOR ENGLISH CLASS 10, Chapter – Julius Caesar

In today’s article, we will focus on the key points of Shakespeare’s Julius Caesar.

Main characters in the play:

• Marcus Brutus: Supporter of the Republic, friend to Caesar.
• Julius Caesar: Great Roman general and Senator.
• Calipurnia: Wife to Julius Caesar.
• Mark Antony: Friend to Caesar, expert orator
• Cassius:A talented general and long time acquaintance of Caesar.
• Decius Brutus: Co-conspirator in Caesar’s assassination.
• Octavius: Caesar’s adopted son and appointed successor.
• Casca: A public figure opposed to Caesar’s rise to power.

Character traits of some important characters:

• Julius Caesar: Nobleman, Courageous, Law-Abiding, Benevolent, Mighty, Credulous.
• Marcus Brutus: Nobleman, Orator, Learned, Easily Instigated, Lack of will power, Democratic, Advocate of Liberty and Freedom.
• Mark Antony: Expert Orator, Loyal, Faithful, Manipulative, Trustworthy.
• Cassius: Main conspirator, Influential, Persuasive, Witty.

Plot Structure:

• Different interpretations of Calipurnia’s dream and Caesar’s decision to not to go to the Capitol.
• Caesar’s arrival at the Capitol and the humble submission of Cimber before Caesar to repeal the verdict on his brother.
• Assassination of Caesar by his conspirators such as Brutus, Cassius and others who shout ‘Liberty, freedom and enfranchisement’.
• Address of the conspirators to the public justifying their act of murdering Caesar.
• Mark Antony’s funeral speech which turned the mob against the conspirators.

Click on the link for chapter summary:
http://cbse.meritnation.com/cbse-english-literature-reader/julius-caesar/371/2242/tutorials.html

Questions you need to focus on to know the core of the lesson:
1. Importance of Antony’s speech in Julius Caesar.
Or,
Compare Antony’s speech with that of Brutus on Caesar’s funeral.
Or,
How did the mob come to know about the plot of the conspirators who killed Julius Caesar?Or,
Discuss Antony as a fantastic orator.
Or,
What reasons does Brutus give for murdering Caesar and how does Antony contradict his views? Explain by contrasting their motives in their respective funeral speeches.
2. Julius Caesar was an ambitious man. Do you agree or disagree? Give reasons for the same.
3. Explain the role of superstitions in Shakespeare’s Julius Caesar.
Or,
Significance of Calipurnia’s dream in the play Julius Caesar.
4. Antony addresses Brutus as “honourable man”. Why? Give reasons.
5. Who was the main person responsible for the conspiracy against killing Caesar? Give reasons from the text.
6.  What role did Decius play in convincing Caesar to go to the Capitol?
7. On what basis did Antony agree to befriend Cassius and Brutus?
8. Justice wins the race. Or, any wrong deed gets punished in the long run. Explain with reference to the play Julius Caesar.
9. Character sketches of Julius Caesar, Mark Antony, Brutus, Cassius and Calipurnia.
10. Theme of democracy in Shakespeare’s Julius Caesar.
11. Who can be justifiably called the tragic hero in the play Julius Caesar? Give your arguments for the same.

Here are a few RTCs from the text which will give you a comprehensive view of the entire chapter:
1. A lioness hath whelped in the streets;
And graves have yawn’d, and yielded up their dead;

2. This dream is all amiss interpreted;
It was a vision fair and fortunate:

3. Our hearts you see not; they are pitiful;
And pity to the general wrong of Rome–

4. Et tu, Brute! Then fall, Caesar.

5. You shall not in your funeral speech blame us,
But speak all good you can devise of Caesar,

6. But Brutus says he was ambitious;
And Brutus is an honourable man.

7. Now let it work. Mischief, thou art afoot,
Take thou what course thou wilt!

8. In every wound of Caesar that should move
The stones of Rome to rise and mutiny.

9 comments February 28th, 2012

English ( Class 10 )

Dear Students,

We are aware of some topics or areas in which students generally experience confusion and doubt in the grammar section. In our articles we are trying to address these. The present article is all about Subject-verb agreement. We are presenting some of the important rules of the same.

SUBJECT-VERB AGREEMENT

A singular subject demands a singular verb. Also, a plural subject demands a plural verb. That is the simple rule which needs to be kept in mind in Subject-verb Agreement.

1. Indefinite pronouns such as everyone and everybody might appear to be plural to few, but they are always singular – and thus take a singular verb.
   • Someone has to take a decision.
   • Everybody is held responsible.
2. Do not be confused by phrases that come between the subject pronoun and its verb- phrases that may contain plural words.
   • Each of the team members in the activity is responsible for writing a team report.
   • Everyone in the entire community is silent on the notion of child marriage.
3. The verb that accompanies pronouns such as all and some will be determined by whether the pronoun is referring to something that is countable or not.
   • Some of the students in the canteen are singing.
   • All the clothes are wet.
   • Some of the grain was ruined.
   • Some of the things which need to be taken care of.
4. None usually seems singular but can be used as a plural pronoun too. The singular verb form is used when “none” means “no one” or “not one”. The plural is used when “none” implies more than one thing or person.
   • None of us thinks what she said is correct.
   • None of the local teams are making it to the second round in the tournament.
5. Phrases such as together with, along with, as well as  seem to join two subjects. However, they do not work the same as ‘and’; they do not work as a conjunction.
   • Some of the notes of the classroom, as well as some from the textbooks, have helped me in my exams.
   • Some of my friends, along with their parents, want to visit the Orange festival.
6. When either or neither  is used as a subject alone (without or or nor), they are singular. This holds true even though the subject seems to be two things.
   • I don’t have any preference between Chocolate and Black Current. Either is fine with me.
   • Neither of these solutions is correct.
7. When either or neither act as correlative conjunctions, the subject that is closer to the verb determines the number of verb, being singular or plural.
   • Neither the principal nor the students are to be blamed.
   • Either the students or the class monitor has to bear the responsibility.

The topic subject-verb agreement, no doubt, poses challenge before the students. However, we hope that having gone through this article you have gained insight and confidence over the same which will help you score good marks in the exam.

Wishing you all the very best!

3 comments February 28th, 2012

Trigonometry and Probability (Class 10)

Let us talk about the sections “Trigonometry” and “Probability”.  Both of these are very interesting and have a great appeal to real life. Together they can  add 14 marks to your treasure. Get through the following material to make the final strategy for this duo.

Probability carries the weightage of 6 marks which can be earned by just applying one formula and that is:

Probability of an event = Number of favorable outcomes / Total Number of Outcomes

The most common experiments which are discussed in the questions are as follows:

Here are few questions which are being repeatedly asked on Ask and Answer on these chapters. Follow the link:

http://www.meritnation.com/discuss/question/1804895/find-the-probability-of-getting-53-sundays-in-a-leap-year

http://www.meritnation.com/discuss/question/561488/what-is-the-probability-of-getting-wednesday-in-a-leap-year

http://www.meritnation.com/discuss/question/446669/find-the-probability-that-a-leap-year-selected-at-random-will-contain-53-sundays

http://www.meritnation.com/discuss/question/1822288/two-dice-are-thrown-simultaneously-what-is-the-probability-that-5-will-come-at-each-one

http://www.meritnation.com/discuss/question/1787592/a-b-take-turns-in-throwing-two-dice-the-first-to-throw-a-sum-1o-being-awarded-show-that-if-a-has-the-first-throw-their-chances-of-winning-i

http://www.meritnation.com/discuss/question/1787435/a-pair-of-dice-is-thrown-3-times-if-getting-of-10-as-a-sum-is-a-success-find-the-probability-distribution-of-number-of-success

Apart from that,  questions like “drawing balls from a bag” are very common. So, make the concept to solve these types of questions to get full marks in Probability.

You can get a brief overview of playing cards from the given table.

Similarly, questions related to “throw of two dice”, maximum outcomes are given below as:

In Trigonometry, there is one chapter in the syllabus i.e., “Heights and Distances”. The most interesting thing about the problems of “Heights and Distances” is that if you are able to draw the correct diagram with the given information then the question can be solved very easily. Apart from that, keep the following things in your mind to handle this section.

1. Always draw figure in exam and mark what all dimensions are given to you. Also, mark the required lengths by h, x or any other variable. This will help you to find the remaining lengths required to put in trigonometric ratios used in triangles formed in figure.
2. The angle of elevation is formed when head to be raised to see the object while the angle of depression is formed when head to be lowered to see the object. Both are made between line of sight and the horizontal line.
3. In questions with two unknown variables, always substitute value of one variable found from one triangle into other. This will help you to find the unknown variables easily.

Prepare well! Be confident!

Best of Luck

Add comment February 27th, 2012

Mensuration (Class 10)

Now, 2nd March is not far away and you must be prepared for the D day. Your syllabus is divided in  six sections Algebra, Geometry, Mensuration, Trigonometry, Coordinate Geometry and Probability. Out of these, each of Algebra and Mensuration contribute 20 marks which means 50% of total marks are covered by these two sections.

If we talk about Mensuration,  here are only two chapters in this section such as “Areas Related to Circles” and “Surface Areas and Volumes”. Both of these chapters come with different varieties of questions, so they need to be taken very seriously.

Few important things which are needed to be taken care of to score well in Mensuration are as follows:

1. Write down all the formulae on a sheet and paste it on your study table to learn all of them by heart.
2. Students find it difficult to find total or curved surface area of combination of solids, so keep it clear in mind that we find the area of the corresponding (curved or whole) surface which can be touched or painted.

For example, let us consider the given solid



This solid is made up of a cube and a hemisphere.

CSA of the solid = CSA of hemisphere
TSA of this solid = TSA of cube + CSA of hemisphere – Area of base of hemisphere
Here, we have subtracted area of base as it is not visible to us and it get added in the area

3. While converting one solid to another remember that the volume of both the solids remain same. So, by equating the volume we can find the dimensions asked in question.
4. Always draw figure in the solution. Do proper labelling as it helps you while calculating area and volume.
5. Take care of values when conversion is being done between two units.
6. To check the area of segment calculated by you is correct or not, you can apply the following formula.

Area of segment =

{ } x2

7. If it is asked to calculate area of sector or segment, you have to find area of minor sector and major segment.
8. Write correct unit in solution. In area, it should always be unit square and in volume, it should always be unit cube. If angle is asked, always write its unit i.e., degree  after the value.

This section demands concentration. So, stay focussed and cross-check your calculations.

Many students know the concept and apply the correct formulae, but a single calculation mistake can deduct the marks.

Best of Luck!

Team Meritnation

3 comments February 27th, 2012