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Science 2008 Question Papers

Q. 8. A compound ‘X’ of sodium is commonly used in kitchen for making crispy pakoras. It is also used for curing acidity in the stomach. Identify‘X’. What is its chemical formula? State the reaction which takes place when it is heated during cooking.

Ans. (i) The compound ‘X’ is sodium hydrogen-carbonate commonly known as baking soda.
(ii) The chemical formula of baking soda is NaHCO₃.
(iii) Action of heat : When sodium hydrogen-carbonate is heated during the cooking of food, it decomposes to give sodium carbonate with the evolution of carbon-dioxide gas.

Sodium hydrogencarbonate (baking soda)	carbonate Sodium	Carbon dioxide	Water

Q. 9. Draw the pattern of magnetic field lines around a straight conductor carrying electric current. Apply right-hand thumb rule to mark the direction of magnetic field.

Ans. Pattern of magnetic field lines around a straight conductor carrying electric current

To find the direction of the field lines, Right-hand thumb rule can be applied. Imagine we are holding the
current-carrying straight conductor in our right hand such that the thumb points towards the direction
of current. The fingers wrapped around the conductor will give the direction of the field lines of magnetic field.

Q. 10. Give reason of the following :
(a) Gold and silver are used to make jewellery.
(b) Carbonate and sulphide ores are usually converted into oxides prior to reduction during the process of extraction.

Ans. (a) Gold and silver are used to make jewellery because .
(i) Gold and silver are the most malleable metals.
(ii) Gold and silver are the most ductile metals.
(iii) Gold and silver do not react with air, water and dil. acids. Therefore these metals do not corrode when exposed to atmosphere.
(iv) Gold does not tarnish and retains its luster for years.

(b) Carbonate and sulphide ores are generally converted into oxides prior to reduction during the process of extraction because it is easier to obtain metals from their oxides than from carbonates or sulphides.

Science 2008 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Compartment Outside Delhi
	All Sets (PDF)				Set 1		Set 1
					Set 2		Set 2
					Set 3		Set 3