Board Paper of Class 10 2009 Science (SET 3) - Solutions

Why does 1 M HCl solution have a higher concentration of H⁺ ions than 1 M CH₃COOH solution?

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

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

How is the induced current in a secondary coil related to current in a primary coil?

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

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

Write the name and chemical formula of the calcium compound used for disinfecting drinking water. How is this compound manufactured?

(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.

Calculate the electric energy consumed by a 1200 W toaster in 20 minutes.

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

(a) What is vinegar?

(b) Describe with a chemical equation, what happens when sodium hydrogen carbonate reacts with ethanoic acid.

(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?

(a) How is the direction of electric current related to the direction of flow of electrons in a wire?

(b) Calculate the current in a circuit if 500 C of charge passes through it in 10 minutes.

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

(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.

(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.