Question

Q3 Answer in a Sentence Or a Word : -

(i) Name the brown coloured gas evolved when lead nitrate crystals are heated in a dry test tube.

(ii) Double displacement reactions are also known as precipitation reactions. Why ?

(iii) State one basic difference between a physical change and a chemical change.

(iv) Zinc liberates hydrogen gas when reacts with dilute Hydrochloric Acid, whereas copper does not. Write the

reason?

(v) How will you indicate the following effect in a chemical equation? A solution made in water.

Q4 Directions (QA to QE) : In the following questions a statement of Assertion is followed by a statement of

Reason. Mark the correct choice as

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e) If both Assertion and Reason are false.

(A) Assertion : Chemical reaction changes the physical and chemical state of a substance.

Reason : When electric current is passed through water (liquid), it decomposes to produce

hydrogen and oxygen gases.

(B) Assertion : In a balanced chemical equation, total mass of the each element towards reactant side

= total mass of the same element towards product side.

Reason : Mass can neither be created nor destroyed during a chemical change.

(C) Assertion : Calcium Carbonate when heated gives calcium oxide and water

Reason : On heating CaCO3, decomposition reaction takes place.

(D) Assertion : White silver chloride turns grey in sunlight.

Reason : Decomposition of silver chloride in presence of sunlight takes place to form silver metal

and chlorine gas.

(E) Assertion : A lead nitrate on thermal decomposition gives lead oxide, brown coloured nitrogen

dioxide and oxygen gas.

Reason : Lead nitrate reacts with potassium iodide to form yellow ppt of lead iodide and the

reaction is double displacement as well as precipitation reaction.​

Answer 1

Answer:

1) Nitrogen dioxide NO2

2)because they are accompanied by the formation of a precipitate.

3)only change the appearance of a substance

4)Copper is less reactive