i. The by product of chloroalkali process is NaOH. NaOH when kept in open air absorbs moisture and turns sticky. Hence, X is NaOH.
• When NaOH is treated with strong acid for example HCl, then neutralisation reaction will occur.
• Neutralisation is a reaction between an acid and a base to give salts and water.
• NaOH being strong base and HCl being strong acid reacts with each other to produce Sodium Chloride (NaCl). This is neutralisation reaction.
The balanced chemical equation is given below:
NaOH + HCl →NaCl + H2O
***note: chloroalkali process is an industrial process in which electrolysis of sodium chloride is done in order to obtain chlorine and sodium hydroxide***
ii. X which is NaOH can be stored in Aluminium container.
Explanation: If we see the reactivity series, we will observe that Sodium is placed above Aluminium which means Sodium is more reactive than Aluminium. Hence, no reaction will take place between NaOH and Al.
i. Rain water conducts electricity whereas distilled water does not because:
• Rain water has certain salts and chemicals dissolved in it.
• When electricity is passed through rain water, the salts and chemicals change into ions.
• These ions are responsible for the conduction of electricity in tap water.
• Whereas distilled water has no such salts and chemicals dissolved in it.
• When electricity is passed through distilled water, no ions are formed. Thus, no conduction of electricity in distilled water.
Hence, due to the presence of dissolved salts in rain water, the rain water conducts electricity and distilled water due to the absence of these salts do not conduct electricity.
ii. We feel burning sensation in the stomach when we overeat because:
• The walls of the stomach release acid HCl.
• This acid is used in the digestion process.
• When the food enters the stomach, this acid is released so that digestion can take place.
• Larger the amount of food, the larger is the acid released.
Hence, due to the formation of HCl in the stomach, we feel a burning sensation.
iii. Tarnished copper vessel regains it shine when rubbed with lemon because:
• Tarnishing of copper vessel takes place because a copper oxide layer is formed on the surface of the vessel.
• The copper oxide is basic in nature.
• When lemon which is acid is rubbed on copper oxide which is a base, neutralisation reaction takes place.
• This reaction nullifies the effect of copper oxide, and the vessel gains its original shine.
Hence, due to neutralisation, the tarnished copper vessel gains its original shine when rubbed with lemon.
iv. The crystals of washing soda change to a white powder on exposure to air because:
• The formula of washing soda is Na2CO3.10H2O.
• The washing soda has 10 molecules of water.
• When it is exposed to air, the crystals of washing soda lose the water of crystallisation.
• This loss of water turns the crystal of washing soda to a white powder.
Hence, due to the loss of water from washing soda, the crystal turns to white powder.
v. An aqueous solution of sodium chloride is neutral, but an aqueous solution of sodium carbonate is basic because:
• Sodium chloride is formed as a result of neutralisation of sodium hydroxide and hydrochloric acid.
• Sodium chloride is a salt containing a strong acid HCl and a strong base NaOH.
• Hence, the aqueous solution of sodium chloride is neutral.
• Sodium carbonate, on the other hand, is a salt of weak acid and a strong base.
• When it is added in water, the amount and power of OH- ions is greater than H + ions.
• Hence, the aqueous solution of sodium carbonate is basic.
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