CBSE Board Students Helpline

CBSE released the scehdule of 2010 exams.It includes the commencing of Class X and Class XII boards also.Below are the dates in a table which includes commencing date of AIEEE and AIPMT entrance exams also. Name of Examination Schedule Class 10 Examination will commence from 1st Working day of March 2010. Detailed datesheet will be announced in last week of December 2009. Class 12 Examination will commence from 1st Working day of March 2010. Detailed datesheet will be announced in last week of December 2009. All India Engineering Entrance Examination (AIEEE) 2010 25th April 2010 (Sunday) All India Pre-Medical/Pre-Dental Entrance Examination 2010 Preliminary Examination: April 03, 2010 Final Examination: May 16, 2010 Saturday, October 24, 2009 It has been a tradition for last 2-3 years to spread rumors about CBSE Examination Date Sheet. Even last year, it was being said that the exams will be conducted in the month of February 2009 as there are General Parliamentary Election in India. ...

INDIAN INSTITUTES OF TECHNOLOGY JOINT ENTRANCE EXAMINATION 2010 (JEE-2010) For admission to undergraduate courses at all IITs, IT-BHU, Varanasi and ISMU, Dhanbad Examination Schedule April 11th, 2010 (Sunday) Paper 1: 09.00 – 12.00 hrs Paper 2: 14.00 – 17.00 hrs Paper-1 and Paper-2 will each have separate sections in Chemistry, Mathematics and Physics. Both papers will be of objective type, designed to test comprehension, reasoning and analytical ability of candidates. Syllabus for this examination will be available on the websites of all IITs. The candidate will have the option of submitting the application form either on-line or off-line. Important dates regarding Application Form and Brochure: On-line application process: Sun. Nov. 01, 2009 – Mon. Dec. 07, 2009 Off-line application process: Mon. Nov. 16, 2009 – Tue. Dec. 1 5, 2009 Last date for receipt of completed hardcopy of application forms at IITs: Sat. Dec. 19, 2009 Further details regarding the application process will be pu...

Q.1 :- Calculate the molarity of 25% by weight of aqueous solution of NaOH. Q.2 :- Calculate the molarity of 6g of CH3COOH solution of 600 m.l. volume. Q.3 :- How will you express the mass percentage of a component of solution? Q.4 :- What does it mean by 10% urea in water by mass? Q.5 :- What does it mean by volume percentage of solution? Q.6 :- What does it mean by 20% acetic aqueous solution? Q.7 :- If you are given with 10% by weight glucose solution. How will you calculate mole fraction of glucose in solution? Q.8 :- What is solubility? Q.9 :- On which factors does solubility depend? Q.10 :- What is the effect of pressure on solubility of gases in liquids? Q.11 :- What is the effect of temperature on solubility of gas in liquids? Q.12 :- How the solubility of a gas in liquids is an exothermic process? Q.13 :- Give an equation for relative lowering of vapour pressure? Q.14 :- Why the vapour pressure of solvent in solution is less than that of the pure solvent? Q.15 :- Derive the fo...

Motion Question Bank Question 1. Calculate the average speed of a train, which covers 120 km in 2 hours. Distance covered by the train = 120 km Answer: Time taken = 2 h Question 2. How far does a car travel in 2.5 h if its average speed is 60 km/h ? Answer: Time taken by the car = 2.5 h Average speed = 60 km/h. Here we have to calculate the total distance covered by the car in 2.5h. Question 3. Convert 1 km/h to m/s. Answer: i.e., Question 4. A carriage moves 30 km in one hour. Calculate its speed in m/s. Is it average or uniform speed? Answer: The speed is average speed. Question 5. You are asked to run in a straight line. If you cover a distance of 5 m in each second, what is your (a) speed (b) velocity? Answer: speed = 5 m/s velocity = 5 m/s along the straight path. Question 6. Draw the velocity time graph of a body moving with uniform velocity of 5m/s. Answer: Question 7. Write the equation of motion connecting S, u, v and a where the symbols have their usual meanings. Answer: Ques...

Probability Test 1) One number is drawn from numbers 1 to 150. Find the probability that it is either divisible by 3 or 5. 2) What is the probability that a letter selected at random in an English book is a vowel. 3) A number was drawn at random from the number 1 to 50. What is the probability that it will be a multiple of 2 or 3 or 10. 4) Suppose that it is 11 to 5 against a person A, who is 38 years of age living till he is 73 and 5 to 3 against a person B now 43 living till he is 78 years. Find the probability that both will die 35 years, hence. 5) A candidate is interviewed for the 3 posts. For the first post, there are 3 candidates, for the second post, there are 4 and for third there are 2. What are the chances that he will get selected? 6) Four cards are drawn without replacement. What is the probability that they are all aces? 7) Find the probability of 53 Sundays in a year selected at random. 8) Two unbiased dice are thrown. Find the probabili...

Sulfuric acid has many uses in industry. The amount of sulfuric acid which a country uses in one year can be a measure of that country's economic development (how modern or wealthy it is). Raw Materials. The raw materials (the things you need) are sulfur, air and water. Sulfur is available from fossil fuels and sulfide ores. When sulfur in fossil fuels is burned it produces sulfur dioxide gas. sulfur + oxygen sulfur dioxide. S(s) + O2(g) SO2(g) Sulfide ores are heated in air to produce the metal oxide and sulfur dioxide gas, for example lead sulfide + oxygen lead oxide + sulfur dioxide. 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) The metal is then extracted from the metal oxide. Sulfur is oxidised in these reactions to become sulfur dioxide. Both reactions are exothermic. The sulfur dioxide gas produced from both of the above methods is used to make sulfur trioxide.

Sulfuric acid has many uses in industry. The amount of sulfuric acid which a country uses in one year can be a measure of that country's economic development (how modern or wealthy it is). Raw Materials. The raw materials (the things you need) are sulfur, air and water. Sulfur is available from fossil fuels and sulfide ores. When sulfur in fossil fuels is burned it produces sulfur dioxide gas. sulfur + oxygen sulfur dioxide. S(s) + O2(g) SO2(g) Sulfide ores are heated in air to produce the metal oxide and sulfur dioxide gas, for example lead sulfide + oxygen lead oxide + sulfur dioxide. 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) The metal is then extracted from the metal oxide. Sulfur is oxidised in these reactions to become sulfur dioxide. Both reactions are exothermic. The sulfur dioxide gas produced from both of the above methods is used to make sulfur trioxide.

Outside of their uses in the chemical industry, common uses of acids are 1) Steel used in construction is acid treated before painting. Dilute sulfuric or hydrochloric acid will remove any surface rust which would otherwise spread under the painted surface. 'Rust remover' used to repair cars is dilute phosphoric acid - H3PO4. 2) Baking powder contains tartaric acid. 3) 'Lime scale' removers contain dilute acids. Try using lemon juice or vinegar (weak acids). Lime scale is calcium carbonate (also called furring). 4) A wasp sting is alkali. It may be neutralised with a weak acid (lemon juice or vinegar).

They have a pH less than 7, see pH. They will turn blue litmus paper red. Hydrochloric acid and sulfuric acid will react with 1) Any alkali or base, see neutralisation. 2) Any metal above hydrogen in the reactivity series. The metal will fizz, giving off hydrogen gas, and leaving the metal salt in solution. It is not safe to put a metal into an acid which is above magnesium in the reactivity series. Any chloride or sulfate can be safely made by reacting the appropriate metal (from lead to magnesium in the reactivity series) with hydrochloric acid to make the chloride or sulfuric acid to make the sulfate. 3) Any metal carbonate or metal hydrogen carbonate. The metal carbonate or metal hydrogen carbonate will bubble giving off carbon dioxide gas, leaving the metal salt and water. Any chloride or sulfate can be made by reacting the appropriate metal carbonate or hydrogen carbonate with hydrochloric acid to make the chloride or sulfuric acid to make the sulfate (see examples).

They have a pH less than 7, see pH. They will turn blue litmus paper red. Hydrochloric acid and sulfuric acid will react with 1) Any alkali or base, see neutralisation. 2) Any metal above hydrogen in the reactivity series. The metal will fizz, giving off hydrogen gas, and leaving the metal salt in solution. It is not safe to put a metal into an acid which is above magnesium in the reactivity series. Any chloride or sulfate can be safely made by reacting the appropriate metal (from lead to magnesium in the reactivity series) with hydrochloric acid to make the chloride or sulfuric acid to make the sulfate. 3) Any metal carbonate or metal hydrogen carbonate. The metal carbonate or metal hydrogen carbonate will bubble giving off carbon dioxide gas, leaving the metal salt and water. Any chloride or sulfate can be made by reacting the appropriate metal carbonate or hydrogen carbonate with hydrochloric acid to make the chloride or sulfuric acid to make the sulfate (see examples).

A weak acid and a strong acid of the same concentration will produce the same amount of product from the same amount of reactant but the weak acid will take longer to do it. The ionisation of a strong acid is complete. A weak acid is only partly ionised. The ionisation of a weak acid is reversible. ethanoic acid (in water) hydrogen ion + ethanoic ion CH3CO2H(aq) H+(aq) + CH3CO2-(aq) The number of hydrogen ions produced by a weak acid is small. When they have reacted with (for example) magnesium more of the ethanoic acid molecules ionise to produce more hydrogen ions and ethanoic ions (see Le Chatelier's Principle). Eventually all of the ethanoic acid molecules ionise to react with the magnesium

When magnesium is put into an acid it will react and produce hydrogen gas (see more information). The more concentrated the acid, the faster the magnesium will react and you will see more bubbles of hydrogen being produced. A strong acid and a weak acid of the same concentration will react at different rates with the same metal. You can see the difference between a strong acid and a weak acid of the same concentration by looking at the reaction with magnesium. The strong acid will react faster and you will see more bubbles of hydrogen being produced. This is because the strong acid has more hydrogen ions present in solution even though it is at the same concentration as the weak acid. A piece of magnesium the same size should be used in both acids for the comparison to be fair. The weak acid will produce the same amount of hydrogen as the strong acid from the same amount of magnesium

The strength of an acid or alkali depends on how ionised it is in water. A strong acid or alkali is completely (100%) ionised. For hydrochloric acid hydrogen chloride (in water) hydrogen ion + chloride ion HCl(aq) H+(aq) + Cl-(aq) All of the hydrogen chloride molecules become hydrogen ions and chloride ions in water (see examples for other strong acids). For sodium hydroxide sodium hydroxide (in water) sodium ion + hydroxide ion NaOH(aq) Na+(aq) + OH-(aq) Sodium hydroxide exists as ions both in water and in the solid. (see examples for other strong alkalis). A weak acid or alkali is only partly (less than 100%) ionised. For ethanoic acid ethanoic acid (in water) hydrogen ion + ethanoic ion CH3CO2H(aq) H+(aq) + CH3CO2-(aq) Some of the ethanoic acid molecules become ions in water but most of them stay as molecules. The reaction is reversible ...

The strength of an acid or alkali depends on how ionised it is in water. A strong acid or alkali is completely (100%) ionised. For hydrochloric acid hydrogen chloride (in water) hydrogen ion + chloride ion HCl(aq) H+(aq) + Cl-(aq) All of the hydrogen chloride molecules become hydrogen ions and chloride ions in water (see examples for other strong acids). For sodium hydroxide sodium hydroxide (in water) sodium ion + hydroxide ion NaOH(aq) Na+(aq) + OH-(aq) Sodium hydroxide exists as ions both in water and in the solid. (see examples for other strong alkalis). A weak acid or alkali is only partly (less than 100%) ionised. For ethanoic acid ethanoic acid (in water) hydrogen ion + ethanoic ion CH3CO2H(aq) H+(aq) + CH3CO2-(aq) Some of the ethanoic acid molecules become ions in water but most of them stay as molecules. The reaction is reversible ...

The three common acids you will find in the laboratory are 1) Hydrochloric acid - HCl(aq) 2) Nitric acid - HNO3(aq) 3) Sulfuric acid - H2SO4(aq) They are all strong acids - see pH. They all ionise in water to form hydrogen ions (H+ ions). 1) HCl(aq) H+(aq) + Cl-(aq) 2) HNO3(aq) H+(aq) + NO3-(aq) 3) H2SO4(aq) H+(aq) + HSO4-(aq) They are all examples of hydrogen compounds with non-metals. Hydrochloric acid is hydrogen chloride (in water). Nitric acid is hydrogen nitrate (in water). Sulfuric acid is hydrogen sulfate (in water). Sulfuric acid is made using the contact process. They are called Mineral Acids because they were originally obtained from minerals in rocks. Oxides of non-metals are acidic, see CO2, NO, SO2. Hydrogen oxide (H2O) is Water - it is neutral, see Water.

In the reaction below ammonia + water ammonium ion + hydroxide ion NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) Ammonia is the base because it gains a hydrogen ion to become an ammonium ion. Water is the acid because it gives away a hydrogen ion (to ammonia) to become a hydroxide ion. base + acid acid + base NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) According to Lowry and Brønsted, water can be an acid or a base depending on the substance reacting with it.

If you look at the reaction below hydrochloric acid + water hydroxonium ion + chloride ion HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) According to Arrhenius, hydrochloric acid is an acid because it produces hydrogen ions in water (hydrogen ions in water become hydroxonium ions). According to Lowry and Brønsted hydrochloric acid is an acid because it is a proton donor. A proton is a hydrogen ion. A proton donor is a substance which gives a hydrogen ion away. If you look at the reaction above hydrochloric acid gives a hydrogen ion to water. A base is a proton acceptor. This means that a base will gain a hydrogen ion. Water is a base when it is put with hydrochloric acid because water will gain a hydrogen ion to become H3O+. acid + base acid + base HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) On the right side of the arrow, H3O+ is an acid because it can give away ...

Arrhenius, Lowry and Brønsted. Arrhenius defined an acid as a substance which produces hydrogen ions written H+(aq) in water (see examples). Lowry and Brønsted defined an acid as a proton donor and a base as a proton acceptor. If you look at the reaction below hydrochloric acid + water hydroxonium ion + chloride ion HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) According to Arrhenius, hydrochloric acid is an acid because it produces hydrogen ions in water (hydrogen ions in water become hydroxonium ions). According to Lowry and Brønsted hydrochloric acid is an acid because it is a proton donor. A proton is a hydrogen ion. A proton donor is a substance which gives a hydrogen ion away. If you look at the reaction above hydrochloric acid gives a hydrogen ion to water. A base is a proton acceptor. This means that a base will gain a hydrogen ion. Water is a base when it is put with hydrochloric acid because water will gain a hydrogen ion to become H...

What is an Acid? An acid is any substance which produces H+ ions or H3O+ ions in water. H+ ions are called hydrogen ions, H3O+ ions are called hydroxonium ions. You will mostly see acids in reactions as forming H+ ions. In reality, H+ is a single proton, and does not exist on its own. It always attaches to something, in water it joins to H2O to form H3O+ ions. This website will use either H+(aq) or H3O+(aq) to mean acid in water.

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A postcard is a small is a small card (5.75x3.75 inches) on which a short message is written and sent by post. On one side of the card, there is blank space for the message which can continue on one half of the other side. The remaining half is for the name and address of the receiver. Language: The postcard is used more for more personal communication than business communication. Therefore, its language is usually informal. There is generous use of informal greeting, contacted form of word and a conversational tone. Contents: while writing postcard, do not include unnecessary details. Do not waste too many words on introduction. Talk more about your experience and feelings and how they have affected you. Show your love, respect and concern for the receiver as the case may be. Write as if you are conversing with receiver and narrating an anecdote to her/him. Salutation and closing: You can begin your postcard with Dear -------- followed by the name of the receiver or simply with a ‘Hi!...

A debate is a contest between two speakers or two groups of the speaker to show skill and ability in arguing. Speakers are required to speak for or against a proposition, a question or a problem. To participate in a debate, one must prepare an out line of the main points in order in which one is going to argue. Every topic/subject has its own vocabulary. These must be learnt. The speaker addresses the chair (Mr. President/Madam), ‘submits’ an argument, ‘appeals’ for sympathetic understanding and support, ‘questions’ the opponent’s views and ‘concludes’ an argument. He also ‘answers’ questions in the rebuttal session. Following expressions can be useful in preparing your own arguments I’d like to raise a question/argue --------- In my Opinion ----------- I’d like to present my view ------------- I would like to draw the attention ---------- I fail to understand ------------ My knowledgeable opponent has submitted that ------------ Do you realize that ------------? The point is ---------...

To tell even a simple story well requires some practice. An uneducated person generally tells a tale badly. He does not mentally look ahead as he tells and plans it out. So he repeats himself, omits important items, which he drags in afterward out of place, and dwells too long on minor details and fails to emphasize the leading points. To write a good story, you must have the whole plot clear in your, and the main points arranged in their proper order. Hints: 1.See that you have a clear idea of the plot of the story in your mind before you begin to write. 2.Follow the outline given; i.e., do not omit any point, and keep to the order in which the points are given in the outline. 3.Be careful to connect the points given in the outline naturally, so that the whole will read well as a connected piece of good communication. Otherwise the whole will be disconnected and jerky. You must use your imagination in filling in the details of action, gesture and conversation that should connect one p...

The word Essay is defined in “The Concise Oxford Dictionary” as “a literary composition (usually prose and short) on any subject.” Properly speaking, it is a written composition giving expression to one’s own personal ideas or opinions on some topic; but the term usually covers also any written composition, whether it expresses personal opinions, or gives information on any given subject, or details of a narrative or description. In fact the word “Essay” is somewhat loosely applied to variety of compositions, from Bacon’s compressed “Essays” on the hand, to those so called “Essays” of Macaulay, some of which are lengthy articles, almost as big as small books, on the other. Characteristics of a Good School Essay: 1.Unity: An essay must be a unity, developing one theme with a definite purpose. The subject must be clearly defined in mind and kept in view throughout. Nothing that is not relevant to it should be admitted to the essay. 2.Order: The essay should follow a certain ordered line ...

ASSIGNMENT ON “WHY DO WE FALL ILL?” HEALTH AND DISEASES 1. Define health. What is the significance of health? State the two factors necessary for individual health. 2. A community cannot be termed ‘healthy’ unless each of its individual is ‘healthy’. Comment on the statement. 3. Enlist various community factors which affect the health of an individual. 4. Comment on the role of poverty in spoiling good health. 5. “Healthy, wealthy and wise” are three words interrelated to each other. Give your opinion on the statement. 6. What do you mean by ‘community health care services’? Name the agency that provides these services. Give any five essential elements included in them. 7. Define disease. ‘Being healthy does not mean being disease free’ – Comment on the statement citing few examples. 8. Differentiate between intrinsic and extrinsic factors which cause disease. Name four intrinsic and four extrinsic disease-causing factors. 9. How does a disease look–like? How is the presence o...

New Delhi, Sep 7 (IANS) The Central Board of Secondary Education (CBSE) will scrap its Class 10 Board exams from 2011 and introduce in its place a nine-point grading system, it was announced Monday. The decision drew mixed response from students, child specialists and school administrators. Human Resource Development Minister Kapil Sibal told a news conference: “There will be no Class 10 board examination from 2011.” The last of the Class 10 CBSE Board examination will take place in March-April 2010. But the minister clarified that the exams would very much take place this academic year. From 2011, the evaluation of the students would be based exclusively on a nine-point grading system. But this will be introduced this academic year itself. “This academic year, there will be both a Board examination and a grading system,” the minister said. Under the new system, there will be nine grades: A1, A2, B1, B2, C1, C2, D, E1 and E2. A1 grade will be considered “exceptional”, A2 will be “excel...