Why should a magnesium ribbon be cleaned before burning in air?

2

(a)

Why is the amount of gas collected in one of the test tubes (electrolysis of water) double of the amount collected in the other? Name this gas.

2

(a)

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

2

(a)

Balance the following chemical equations.
(a) HNO₃ + Ca(OH)₂ \(\rightarrow\) Ca(NO₃)₂ + H₂O
(b) NaOH + H₂SO₄ \(\rightarrow\) Na₂SO₄ + H₂O
(c) NaCl + AgNO₃ \(\rightarrow\) AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ \(\rightarrow\) BaSO₄ + HCl

2

(a)

Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide \(\rightarrow\) Calcium carbonate + Water
(b) Zinc + silver nitrate \(\rightarrow\) Zinc nitrate + Silver
(c) Aluminium + Copper chloride \(\rightarrow\) Aluminium chloride + Copper
(d) Barium chloride + Potassium Sulphate \(\rightarrow\) Barium sulphate + Potassium chloride

2

(a)

Why do we apply paint on iron articles?

2

(a)

A yellowish coloured compound 'A' is photosensitive material. On exposure to sunlight, it gives a greyish substance 'B' and brown fumes of a gas 'C'. Identify A, B and C. How will you obtain A from the nitrate salt of B?

2

(a)

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitrate.
(c) Chloride gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.

2

(a)

During the reaction of some metals with dilute hydrochloric acid, following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium(Al) is added.
(c) The reaction of sodium metal is found to be highly explosive
(d) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explain these observations given suitable reasons.

2

(a)

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why.

2

(a)

How can you chemically remove the black coating of copper oxide?

2

(a)

Why is photosynthesis considered as endothermic reaction?

2

(a)

Give an example of a decomposition reaction. describe an activity to illustrate such a reaction by heating.

2

(a)

Translate the following statement into chemical equation and then balance it: ''A metal in the form of ribbon burns with a dazzling white flame and changes into a white powder'.

2

(a)