Question

State the type of chemical reaction in each of the following: [1x4]
i) When electric current is passed through water, hydrogen and oxygen gases are
produced.
ii) When oxygen is passed over red, hot copper, copper oxide is produced.
iii) Calcium carbonate produces calcium oxide and carbon dioxide on heating.
iv) Calcium reacts with water to give calcium hydroxide and hydrogen gas.

Answer 1

Answer:

• When electric current is passed through water, water dissociates into hydrogen and oxygen. Hydrogen is deposited over negative pole and oxygen is deposited over positive pole. Deposition of hydrogen and oxygen at different poles is visible in the form of bubbles
• sometimes develop your own equations in a step by step manner. it’ll never go wrong. just follow the steps one by one.
• first write the equation;
• 2H + CuO → Cu + H2O.
• Now balance the equation. [i m directly doing above].
• and we know the physical states don’t we?
• you’ve mentioned it yourself.
• 2H(g) + CuO(s) → Cu(s) + H2O (g).
• CuO and Cu can niether be in g nor in l state
• Decomposition of Calcium Carbonate
• At 1200K, calcium carbonate decomposes to give carbon dioxide and calcium oxide. When heated, calcium carbonate decomposes into calcium oxide and carbon dioxide. This process is employed in the manufacturing of quick lime, which is an important substance in many industries.
• Reaction of calcium with water
• The reaction forms calcium hydroxide, Ca(OH)2 and hydrogen gas (H2). The calcium metal sinks in water and after an hour or so bubbles of hydrogen are evident, stuck to the surface of the metal.