CBSE Guess > Papers > Question Papers > Class X > 2009 > Science > Science

Q. 13. (a) What are salts among chemical substances? Give an example of a salt derived from a strong acid and a weak base. State the behaviour of aqueous solution of this salt towards litmus solution.
(b) Why does hydrogen chloride gas not show acidic behaviour? 3

Ans. (a) A salt is a compound formed by the reaction between an acid and a base. Ammonium chloride (NH₄Cl) is a salt of a strong acid, hydrochloric.acid (HCl), and a weak base, ammonium hydroxide (NH₄OH). This salt is acidic in nature therefore it turns blue litmus red.

(b) The acidic behaviour of acids is due to the presence of hydrogen ions, H+ (aq) ions in them. The acids produce hydrogen ions only in the presence of water. So, in the absence of water, a substance will not form hydrogen ions and hence will not show its acidic behaviour. So HCl gas does not show acidic behaviour.

Q. 14. Draw a circuit diagram to show an electric lamp of resistance 30  and a resistor of 6 connected in series with a battery of 6 V. Calculate
(a) total resistance in the circuit
(b) current flowing through the circuit
(c) potential difference separately across the lamp and the resistor. 3

Sol.

Science 2009 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Outside Delhi		Foreign
	Set 1 (PDF)		Set 1 (PDF)		Set 1		Set 1		Set 1 (PDF)
					Set 2		Set 2
					Set 3		Set 3