27. Write the chemical reaction for the followings: -
How Sodium reacts with water
Formation of Carbonic acid
(iii) Formation of Sulphur dioxide and Sulphurous acid
(iv)
Corrosion of Copper
How Aluminum reacts with Hydrochloric acid
(vi) How Copper and Silver reacts with Conc. Sulphuric acid
Answers
Answer:
1) Sodium metal reacts rapidly with water to form a colourless solution of sodium hydroxide (NaOH) and hydrogen gas (H2). The resulting solution is basic because of the dissolved hydroxide.
2) Carbonic acid is a weak acid that's formed from the reaction of carbon dioxide dissolved in water.
3)Sulfur dioxide, SO2, is a colorless gas or liquid with a strong, choking odor. It is produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores (aluminum, copper, zinc, lead, and iron) that contain sulfur.
Sulfurous acid is found in nature as an intermediate in the formation of acid rain, by the reaction of sulfur dioxide with atmospheric moisture.
4)Copper corrosion is the corrosion of materials made of copper or copper alloys. When exposed to the atmosphere, copper oxidizes, causing bright copper surfaces to tarnish. After a few years, this tarnish gradually changes to dark brown or black, and finally to green.
5)Aluminum Reacts With Hydrochloric Acid To Produce Aluminum Chloride And Hydrogen Gas.
6) Silver does not react with dilute hydrochloric acid and dilute sulphuric acid but it reacts with hot concentrated sulphuric acid and this reaction gives sulphur dioxide water and silver sulphate.
Copper does not react with dilute sulphuric acid as its reduction potential is higher than that of hydrogen.
Explanation:
1) The reaction is exothermic. During the reaction, the sodium metal may well become so hot that it catches fire and burns with a characteristic orange colour. The reaction is slower than that of potassium (immediately below sodium in the periodic table), but faster than that of lithium (immediately above sodium in the periodic table).
2Na(s) + 2H2O → 2NaOH(aq) + H2(g)
2)keep in mind that the production of carbonic acid in nature is often spontaneous and in small amounts. No need to panic; carbonic acid isn't randomly floating around in our air. However, through the combination of water and carbon dioxide in the atmosphere, carbonic acid can be formed. This actually explains why we may find small amounts of this acid in rainwater.
H2O (water) + CO2 ( carbon dioxide) → H2CO3 ( carbonic acid )
Therefore, this reaction is also reversible.
3)Sulphur dioxide is usually made in the laboratory by heating concentrated sulphuric acid with copper turnings.
Cu+2H2SO4—-HEAT—–>CuSO4+SO2+2H2O
Sulfurous acid is prepared by dissolving sulfur dioxide in water. However, the reaction is reversible and the acid readily decomposes back into the reactants.
SO2 + H2O → H2SO3
4)When copper or silver combines with oxygen, the process is known as corrosion or oxidation. When copper reacts with oxygen, then it produces copper oxide. The chemical equation of this reaction is 4Cu + O2 = 2Cu2O, and forms Copper Oxide.
5)2Al(s) + 6HCl(aq) -> 2AlCl3(aq) + 3H2(g)
6)But, concentrated sulphuric acid is an oxidising agent. So, when copper is heated with conc.H2SO4, a redox reaction occurs and the acid gets reduced to sulphur dioxide.
Cu + 2H2SO4 = CuSO4 + SO2 + 2H2O