SCIENCE CLASS 10 CHAPTER -1 CHEMICAL REACTION AND EQUATIONS QUESTION 1. Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO2 2 (g) (a)Lead is getting reduced. (b)Carbon dioxide is getting oxidised. (c)Carbon is getting oxidised. (d)Lead oxide is getting reduced. (i)(a) and (b) (ii)(a) and (c) (iii)(a), (b) and (c) (iv)all ANSWER (i)(a) and (b) QUESTION 2. Fe 2 O 3 + 2Al → Al 2 O 3 + 2Fe The above reaction is an example of a (a)combination reaction. (b)double displacement reaction. (c)decomposition reaction. (d)displacement reaction. ANSWER (d)displacement reaction. QUESTION 3. What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. (a)Hydrogen gas and iron...
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CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 15 (a) With the help o suitable circuit diagram prove that the reciprocal of equivalent resistance of a group of resistances joined in a parallel is equal to the sum of the reciprocals of the individual resistances. (b) In an electric circuit two resistors of 12 ohm are joined in parallel to a 6V battery. Find the current drawn from the battery. ANSWER NO. 15 There resistors R 1 , R 2 and R 3 are connected in parallel. The total current I, is equal to the sum the separated currents through each resistor R 1 , R 2 and R 3 . I = I 1 + I 2 + I 3 ----------------------------(1) Let Rp be the equivalent resistance of the parallel combination of resistors. By applying ohm's law to the parallel combination of resistors. I = V/Rp ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 17 An electric lamp of resistance 20 ohm and a conductor of resistance 4 ohm are connected to 6V battery as shown in the circuit. (a) the total resistance of the circuit (b) the current through the circuit (c) the potential difference across the (i) electric lamp (ii) conductor (d) power of the lamp. ANSWER NO. 17 (a) Voltage of battery V = 6 volt Resistance of electric lamp R 1 = 20 ohm Resistance of conductor = 4 ohm Total resistance R = R 1 + R 2 = 20 + 4 = 24 ohm (b) According to ohm's law = V = IR ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 13 Compare the power used in 2 ohm resistor in each of the circuit. ANSWER NO. 13 (i) Potential difference V = 6 V Since 1 ohm and 2 ohm resistance are connected in series hence, equivalent resistance of the circuit R = 1 + 2 = 3 ohm According to ohm's law - V = IR, I = V/R = 6/3 = 2A Power used in 2 ohm resistance = P = IIR = 2X2X2 = 8 watt (ii) Since 1 ohm and 2 ohm resistors are connected in parallel. The voltage across each component of a parallel circuit remains the same. Hence the voltage across 2 ohm resistor will be 4V. Power consumed by 2 ohm resistor is P = VV/R = 4X4/2 = 8 watt QUESTION NO. 14 (a) Name and state the rule to determine the direction of force experienced by the a current carrying straight conductor placed in a uniform...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 55 A coil of insulated copper wire is connected to a galvanometer. What would happen if a strong bar magnet is. (a) Pushed into the coil ? (b) Withdrawn from inside the coil ? (c) Held stationary inside the coil ? Give justification for each observation. ANSWER NO. 55 (a) When a bar magnet is pushed into the coil of insultated copper wire connected to a galvanometer, an induced current is set u in the coil due to change of magnetic field through it. As a result, galvanomter gives a deflection. (b) When the bar magnet is withdrawn from inside the col, again an induced current is setup in the coil due to change of magnetic field through it . As a result galvanometer gives a deflection in the reverse direction. (c) If the bar magnet is held stationary inside the coil, then there is no induced current in the coil, because there is no change in magnetic field through i...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 7 (i) write the step involved in the extraction of pure metal in the middle of activity series from their carbonate ore. (ii) how is copper extracted from its sulphide Ore? Explain the various steps supported by chemical equation. (iii) explain the process of electrolytic refining of copper. ANSWER NO.7 (i) the metals in the middle of the activity series such as iron, lead and copper are moderately reactive. These are usually presented as sulphide or carbonate in nature. Carbonate Ores are changed into oxides by heating strongly in limited air. This process is known as calcination of the chemical reaction of calcination of carbonate ore are as follows - ZnCO 3 ------------------> ZnO + CO 2 The metal oxide are then reduced to metal by using suitable reducing a...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO.9 (a) List four characteristics of the image formed by plane mirrors. (b) A 50 cm tall object is placed at a distance of 20 cm from a concave mirror of focal length 30 cm. Use mirror formula to determine position and size of the image formed. ANSWER NO.9 (a) Image is virtual and erect. The size of the image is equal to that of the object. The image formed is as far behind the mirror as the object is in front of it. The image is laterally inverted. (b) Height of object = 5 cm u = - 20 cm f = - 30 cm Using mirror formula 1/f = 1/v + 1/u 1/- 30 = 1/v + 1/- 20 1/-30 - 1/-20 = 1/v 1/-30 + 1/20 = 1/v -2+3/60 = 1/v 1/60 = 1/v v= 60 cm ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 45 What is the cause of dispersion of white light through glass prism ? Draw a ray diagram to show the path of light when two indentital glass prism are arranged together in inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prism. ANSWER NO. 45 DISPERSION The splitting of light into its component colour is called dispersion. CAUSES OF DISPERSION OF LIGHT When light passes through a prism, the different frequencies of light travel at different velocities. Because of refraction, the different velocities make the angle of refraction different, causing the light to travel in slightly different direction. QUESTION NO. 46 Write the function of the following in human eye. (i) Cornea (ii) Retina (iii) Iris ANSWER NO. 46 (i) CORNEA Light enters the eye ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 40 Law of reflection of light. Define absolute refractive index and Express it mathematically. ANSWER NO. 40 LAW OF REFLECTION The angle of incidence is equal to the angle of reflection. The incident Ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane. REFRACTIVE INDEX Refractive index is a number which measures the bending of light when passing from one medium to another. It is the ratio of velocity of light in vacuum to the velocity of light in the medium. Refractive index = velocity of light in vacuum velocity of light in medium QUESTION NO. 41 Define the following and show in the diagram. Centre of curvature Pole Radius of curvature of the mirror Pri...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 50 Define the term power of accommodation. Write the modification in the curvature of the eye lens which enables us to see the nearby object clearly. ANSWER NO. 59 POWER OF ACCOMMODATION The ability of eye lens to adjust it's focal lenght is called accommodation. The eye lens lens is composed of a fibrous, jelly - like material. It's curvature be modified to some extent by the ciliary muscles. When we look at objects closer to the eye, the ciliary muscles contract. This increases the curvature of the eye lens. The eye lens then becomes thicker. The focal length of the eye lens decreases. This enable us to see nearby object clearly. QUESTION NO. 51 When do we consider a student sitting in the class to be myopic ? List two causes of this defect. Explain using a ray diagram how this defect of eye can be corrected. ANSWER NO. 51 In myopic conditi...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 11 1. Isomers define. 2. Draw two possible isomers of the compound with molecular formula C3 H6O and write their names. 3. Differentiate East verification and saponification on the basis of chemical equation. ANSWER NO. 11 1. ISOMERS : the compound which have identical molecular formula but different structure are called isomers. 2. 3. ESTERIFICATION REACTION : Ester are most commonly formed by reaction of an acid and alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst give and ester. SAPONIFICATION : On heating with Sodium Hydroxide, which is an alkali, the step is converted back to alcohol and sodium salt of carboxylic acid. This reaction is known as saponification. QUESTION NO. 12 What is methane ? Draw it electron dot structure name the type types of bonds formed in this compound fullstop wh...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 3 The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. (a) List one advantage and one limitation of al the three attempts. (b) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass. (c) State modern periodic law. ANSWER NO. 3 (a) ADVANTAGE OF DOBEREINER - Chemists look at elements in terms of groups of elements with similar chemical chemical and physical property. DISADVANTAGE All the known elements could not be arranged in the form of triad. ADVANTAGE OF NEWLAND Newland law of octaves was the first logically bases on the atomic weight. DISADVANTAGE New land could arrange element only upto calcium, out of the total 56 elements known. ADVANTAGE OF MENDELLEV Arrange the 63 known elements i...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 6 Why is respiration considered an exothermic reaction ? Explain. ANSWER NO. 6 During digestion, food is broken down into simpler substance. Carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cell of our body and provides energy. The special name of this reaction is respiration. QUESTION NO. 7 Write the importance of PH in everyday life. ANSWER NO. 7 1. Our digestive system - Hydrochloric acid produced in our stomach helps the digestion of food. But when the amount of acid goes beyond a certain limit you to indigestion, pain and irritation are created. To neutralize if that of excess acid magnesium Hydroxide (milk of magnesia) is a my base used as antacid. 2. Acid cause tooth decay : Tooth decay starts when the pH of mouth is lower than 5.5. The best way to prevent this clean the mouth after eating. 3. To determine t...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 5 (a) How is valency of element determined if its electronic configuration is known ? Determine the valency of an element of atomic no.9 . (b) Given below are some elements of the modern periodic table. Atomic number of the elements are given in parenthesis: A(4), B(9), C(14), D(19), E(20) (i) With the help of electronic configuration, find out which one of the above element will have one electron in its outermost shell. (ii) Which two elements belongs to the same group ? Give reasons for your aswe. (iii) Which one of the above element belonging to the fourth period has bigger atomic radius and why ? ANSWER NO.5 (a) An elements valency is determined by the number of electrons in its outer shell. Hence, the number of valence electrons obtained from the electronic configuration of the element gives the valency i.e. the number of electrons lost, gained or ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION QUESTION NO. 16 An ore on treating with dilute hydrochloric acid produce brisk effervescene. Name the type of ore with one example. What step will be required to obtain metal from the enriched ore ? Also write the chemical equation for reaction involved in this process. ANSWER NO. 16 Type of ore is carbonate ore. The following steps required to obtain pure metal from this ore. 1. Calcination, to obtain oxide of the metal. 2. Reduction, reacting the oxide of metal with carbon monoxide. 3. As a result pure metal is be obtained. ZnCO 3 ---------------------> ZnO + CO 2 ZnO + CO ---------------> Zn+ CO 2 QUESTION NO. 17 When copper powder is heated in China dish the reddish brown surface of copper powder becomes coated with a black substances. (a) why has the black substance formed? (b) what is this black substance ? (c) write the che...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5 FOR BOARD EXAMINATION QUESTION NO. 1 What is difference between soap and detergent? State in brief the cleansing action of soap in a movie and always got from a fabric. Why are so are not very effective when fabric is washed in hard water? How is this problem resolved. ANSWER NO.1 Soaps are sodium salt of long chain carboxylic acid. Whereas detergents are sodium salt of long chain benzene sulphonic acid. Detergents are soluble in hard water, whereas so do not work in hard water. Dirts are oily in nature, all does not dissolve in water. The molecules of soap are Sodium and potassium salt of long chain carboxylic acid. The ionic end of soap interact with water while the carbon chain interact with oil. The soap molecules, thus form structures called micelles where one end of the molecules towards the oil droplet while the ionic end faces outside. This form and ...
CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 1 FOR BOARD EXAMINATION QUESTION NO. 101 What are outside raw materials used for an organism? ANSWER NO. 101 1. WATER : which is used for digestion of food and also useful for certain body function. 2. OXYGEN : oxygen is useful for breakdown of food which provide energy and it is very essential for in organism to live. 3. FOOD : it is obligatory source of energy for a body. QUESTION NO.102 What is role of the acid in our stomach? ANSWER NO. 102 Stomach acid activates the enzyme pepsin needed for protein digestion. Stomach acid signals to the pancreas to produce digestive juices and enzymes to further breakdown of food. QUESTION NO. 103 What is the function of digestive enzymes? ANSWER NO. 103 Digestion is set of biochemical reaction. Digestive enzymes are bio catalyst which can increase the rate of biochemical reaction. QUESTION NO. 104 Write the names of enzyme secreted by Mout...