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CBSE class 10 science most important questions and answers -Part 3
Here, CBSE class 10 science most important questions and answers -Part 3 for 2020-21 CBSE Board part III published by Future Study Point are presented for the students of 10 class who are going to appear in the 2021-22 CBSE board exam. CBSE class 10 science most important questions and answers for 2021-22 board-III are designed by the expert of the subject and their answers are readily explained in an ordered way.
CBSE class 10 science most important questions and answers for 2020-21 board-III are designed as per the updated syllabus of CBSE, so you need not to have any kinds of doubt in the selections of the questions. The most important questions of science for class 10 are taken from the last year’s science question papers of class 10, these most important questions of science are the questions of last year’s questions papers of class 10 science which are asked frequently,so the students are required to pay special attention to the solutions of these questions for achieving maximum percentage in a science subject.
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- Increases science skill
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- Helpful to get additional marks in science
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CBSE class 10 science most important questions and answers -Part 3
Q1. Write a balanced chemical equation for the reactions that take place during respiration. Identify the type of combination reaction that takes place during this process and justifies the name. Give one more example of this type of reaction.
Ans. The respiration process is a combination reaction in which oxygen inhaled by us reacts with the glucose which exists in each cell of the organism because carbohydrate is taken by us ultimately is broken down into glucose. Oxygen combined with this glucose molecule produces carbon dioxide, water, and energy in the form of ATP. The respiration process is given by a chemical equation as follows.
The type of reaction is exothermic because with the products, energy is also released.
Another example of an exothermic chemical reaction is calcium oxide combines with water releases calcium hydroxide along with heat energy.
Note-Many of the students may have doubts that respiration reaction is called here a combination reaction, if we explain glucose is broken down into carbon dioxide and water then it can be assumed decomposition reaction but from another angle, you say that glucose combines with oxygen releases main product carbon dioxide along water and heat then it can be called combination reaction.It is up to illustration to assume respiration reaction as a combination or decomposition reaction.
Q2. A small amount of quick lime is added to the water in a beaker.
(a)Name and define the type of reaction that has taken place.
(b) Write a balanced chemical equation for the above reaction. Write the chemical name of the product obtained.
(c) State two observations that you will make in the reaction.
Ans. (a) The type of chemical reaction is a combination reaction and a subtype of this reaction is an exothermic reaction because heat is evolved during the reaction, the combination reaction is the type of chemical reaction in which two substances react together forms single substance.
(b) The reaction when quick lime is added to water is shown bellow.
Calcium oxide Calcium hydroxide
The chemical name of the product obtained i.e slaked lime or lime water is Calcium hydroxide.
(C) Two observations are seen during this reaction are the following.
(i) A hissing sound is emitted during the reaction.
(ii) A large amount of heat is produced during chemical reaction.
Q3.On heating green coloured crystals, a gas with a characteristic
odour of burning sulphur evolves and the colour of crystals change.
(i) Name the gas evolved with its chemical formula.
(ii) Identify the green crystals.
Ans. (i and ii) Green coloured crystals are of hydrated ferrous sulphate i.e FeSO4.7H2O When it is heated changed into anhydrous ferrous sulphate(white colour) thereby it is broken down into ferrous oxide(brown colour), sulphur dioxide and sulphur trioxide,a gas with a characteristic odour of burning sulphur evolves is SO2.
During the reaction, the so formed SO3(sulphur trioxide) is a gas found in solid-state in room temperature.
Q4.“Combination reaction is the reverse of decomposition reaction”. Justify this statement with the help of appropriate chemical equation for each.
Ans. The combination reaction is in which two or more than two compounds or elements form a single compound. As an example, carbon and oxygen combine together forms carbon dioxide.
The decomposition reaction is exactly opposite to the combination reaction because in it one compound breaks down into two or more than two compounds. As an example calcium carbonate, when heated converted into calcium oxide and CO2 .
Q5 Naman and Raghav perform an experiment in which they mix concentrated sulphuric acid with water. Naman mixes water to acid and Raghav mixes acid to water slowly with constant stirring. Mention the suitable reason for selecting the one which you find is a correct method and discarding the one which is wrong.
(a) Compare the properties of a typical metal and a non-metal on the basis of the following :
(i) Nature of the oxide formed by them
(ii) Conductivity
(b) Name a non – metal which is lustrous and a metal which is liquid at room temperature.
Ans. When acid and water are mixed together ions are formed in which a lot of heat releases, in other words, it is an exothermic reaction.
The way of Naman mixing water to acid is quietly wrong, in this way a large amount of heat will be generated, In this method, it takes more time to dilute the acid,initially, there is less water to react with larger proportion of sulphuric acids so the excess amount of heat boils the solution which may splash out of the container harming the person doing this practice and the person near about him.
Raghav mixes acid to water with stirring the whole mixture is the right way of diluting the acid, the reaction is slower than the reaction occurs when water added to acid because in this case, little acid reacts with more water, so the heat generated will be lesser.
Ans.(a) (i) The oxides are formed as a result of a combination of non-metals or metals with oxygen.
Non-Metalic oxide – These are generally gases in room temperature, the few examples are given below.
Generally, the solution of non-metallic oxide with water is acidic in nature, it is that’s why acid rain is caused by the reaction of SO2 with water forming sulphuric acid and reaction of NO2 with water forming HNO3 acid.
Metallic oxide – The metallic oxide may be either of basic in nature or it may have both characters of basic as well as of acidic, these are formed when metal combines with oxygen.
The sodium oxide reacts with HCl produces salt shows its basic nature while aluminum oxide reacts with acids as well as with base produces salts of a different kind which shows nature of aluminum oxides basic as well as acidic in nature such oxides which have basic and acidic nature known as amphoteric oxides.
(ii) Atoms of metals are not bounded by any bonds like covalent or ionic bonds like non-metals, so their electrons are free to move within the metal which causes them to be a conductor of heat and electricity. While electrons in non-metals are bounded by the strong electrostatic force exerted by a covalent or ionic bond making them a bad conductor of heat and electricity.
(b) Graphite is the only non-metal which is lustrous and mercury is the only metal that is found in the liquid state at room temperature.
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