10th Science Paper Solutions Set 2 : CBSE All India Previous Year 2009

General Instructions:
(i) The question paper comprises of two sections, A and B. You are to attempt both the sections
(ii) All questions are compulsory
(iii) There is no overall choice. However, internal choice has been provided in all the three questions of five marks category. Only one option in such questions is to be attempted
(iv) All questions of Section A and all questions of Section B are to be attempted separately
(v) Questions number 1 to 6 in Section A and 17 to 19 in Section B are short answer type questions. These questions carry one mark each
(vi) Questions number 7 to 10 in Section A and 20 to 24 in Section B are short answer type questions and carry two marks each
(vii) Questions number 11 to 14 in Section A and 25 and 26 in Section B are also short answer type questions and carry three marks each
(viii) Questions number 15 and 16 in section A and question number 27 in section B are long answer type questions and carry five marks each
Q1 :

What happens when a small piece of sodium is dropped into ethanol?


Answer :

When a small piece of sodium is dropped into ethanol, sodium reacts with ethanol to give sodium ethoxide. Hydrogen gas is evolved in the process. This reaction can be represented by the following equation.

Q2 :

Which one of these has a higher concentration of H+ions?

1 M HCl or 1 M CH3COOH


Answer :

HCl is a stronger acid than CH3COOH. When added to water, HCl dissociates almost completely to give H+ions. In contrast, in the case of CH3COOH, only partial ionisation occurs. This is why 1 M HCl solution has a higher concentration of H+ions than 1 M CH3COOH solution.

Q3 :

In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?


Answer :

The balanced chemical equation for the electrolysis of water is:

It can be observed from the balanced chemical equation that the volumes of hydrogen and oxygen produced during electrolysis are in the ratio 2: 1. Thus, the volume of hydrogen gas collected in the process is double than that of oxygen.

Q4 :

State the rule which gives the direction of magnetic field associated with a current-carrying conductor.


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Q5 :

Define the term ‘induced current’.


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Q6 :

Draw a schematic diagram of an electric circuit consisting of a battery of two cells each of 1.5 V, 5 Ω, 10 Ωand 15 Ωresistors and a plug key, all connected in series.


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Q7 :

Crystals of copper sulphate are heated in a test tube for some time 

(a)  What is the colour of copper sulphate crystals 

    (i) before heating, and

(ii) after heating? 

b) What is the source of liquid droplets seen on the inner upper side of the test tube during the heating?


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Q8 :

(i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

(ii) What type of reaction is this?

(iii) Write a balanced chemical equation to represent the above reaction.


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Q9 :

A lamp rated 100 W at 220 V is connected to the mains electric supply. What current is drawn from the supply line if the voltage is 220 V?


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Q10 :

What is an electric circuit? Distinguish between an open and a closed circuit.


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Q11 :

(a) What is a homologous series of substances?

(b) In an organic compound, which parts largely determine its physical and chemical properties?

(c) Write a chemical equation to represent the reaction of ethanol with acidified solution of potassium dichromate?


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Q12 :

(a) What is meant by periodicity in properties of elements with reference to the periodic table?

(b) Why do all the elements of the same group have similar properties?

(c) How will the tendency to gain electrons change as we go from left to right across a period? Why?


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Q13 :

(a) Define the term ‘coulomb’.

(b) State the relationship between the electric current, the charge moving through a conductor and the time of flow.

Calculate the charge passing through an electric bulb in 20 minutes if the value of current is 200 mA.


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Q14 :

For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.


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Q15 :

(a) Distinguish between ionic and covalent compounds under the following properties:

(i) Strength of forces between constituent elements

(ii) Solubility of compounds in water

(iii) Electrical conduction in substances

(b) Explain how the following metals are obtained from their compounds by the reduction process:

(i) Metal M which is in the middle of the reactivity series.

(ii) Metal N which is high up in the reactivity series.

Give one example of each type

OR

(a) Distinguish between ‘roasting’ and ‘calcination’. Which of these two is used for sulphide ores and why?

(b) Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.

(c) Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure copper.


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Q16 :

(a) What is myopia? State the two causes of myopia. With the help of labelled ray diagram, show

(i) The eye defect myopia

(ii) Correction of myopia using a lens.

(b) Why is the normal eye unable to focus on an object placed within 10 cm from the eye?

OR

(a) What is dispersion of white light. What is the cause of such dispersion. Draw a diagram to show the dispersion of white light by a glass prism.

(b) A glass prism is able to produce the spectrum when white light passes through it, but a glass slab doesn’t produce any spectrum. Explain why it is so.


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Q17 :

Why are green plants called ‘Producers’? 


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Q18 :

Why is DNA copying an essential part of the process of reproduction?


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Q19 :

Which compounds are responsible for the depletion of ozone layer?


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Q20 :

Describe how hydro-energy can be converted into electrical energy. Write any two limitations of hydro-energy.


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Q21 :

How is charcoal obtained from wood? Why is charcoal considered a better fuel than wood?


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Q22 :

Describe the role of the following in human beings:

(i) Seminal vesicles

(ii) Prostate gland


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Q23 :

An environmentalist on visit to your school suggested the use of three R’s to save the environment. Explain what he meant by three R’s and how you would follow his advice at home.


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Q24 :

What isChipko movement? Why should we conserve forests?


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Q25 :

Explain how the sex of the child is determined at the time of conception in human beings.


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Q26 :

What is ‘hydrotropism’? Describe an experiment to demonstrate ‘hydrotropism’’?


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Q27 :

(a) Draw a sectional view of the human heart and label on it Aorta, Pulmonary arteries, Vena cava, Left ventricle.

(b) Why is double circulation of blood necessary in human beings?

OR

(a) Draw the structure of a nephron and label the following on it: Glomerulus, Bowman’s capsule, Renal artery, Collecting duct.

(b) What happens to glucose that enters the nephron along with filtrate?


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10th Science Paper Solutions Set 3 : CBSE Delhi Previous Year 2013 will be available online in PDF book soon. The solutions are absolutely Free. Soon you will be able to download the solutions.