NCERT Page Number – 25
Question: 1:- Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
HCl, HNO3, etc. form hydronium ions in aqueous solutions while alcohol and glucose do not dissociates hydronium ion in the solution instead they contain hydrogen.
Hence, HCl, HNO3, etc show acidic characters in aqueous solution while solutions of compounds like alcohol and glucose do not.
Question: 2:- Why does an aqueous solution of an acid conduct electricity?
Acid dissociates ions in aqueous solution, which conducts electricity.
Question: 3:- Why does dry HCl gas not change the colour of the dry litmus paper?
Because dry HCl gas does not contain hydronium ions. Hence, it does not changes the colour of dry litmus paper.
Question: 4- While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
When acid is mixed with water it evolves heat. The reaction takes place in this process is exothermic.
If water is mixed with acid, then because of presence of large amount of acid, more heat would be evolved, which may splashes out and can be resulted into accident due to burning.
Therefore, it is recommended that the acid should be added to water and not water to the acid.
Question: 5- How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?
The concentration of hydronium ions (H3O+) decreases when a solution of an acid is diluted.
Q 6- How is the concentration of hydroxide ions (OH-) affected when excess base is dissolved in a solution of sodium hydroxide?
The concentration of hydroxide ions increase when excess base is dissolved in a solution of sodium hydroxide.
NCERT Page Number – 28
Q -1- You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
An acidic solution has pH value less than 7 and a basic solution has pH value more than 7.
Hence, the solution A having pH value is 6 is acidic consequently has more hydrogen ion concentration. The solution B which has pH value is 8 is basic solution.
Q -2- What effect does the concentration of H+(aq) ions have on the nature of the solution?
The concentration of H+ (aq) ions determines the acidic nature of solution. Hence, acidity of a solution increases with increases in concentration of H+ (aq) ions and vice versa.
Q -3- Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Yes basic solutions also have H+(aq) ions. They are basic because the concentration of hydroxide (OH-) is more than the H+(aq) ions.
Q -4- Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
If the soil is acidic then it should be treated with quick lime or slaked lime to make it neutralize so that soil can be made proper for cultivation.
NCERT Page Number – 33
Q -1- What is the common name of the compound CaOCl2?
Common name of CaOCl2 is bleaching powder.
Q -2- Name the substance which on treatment with chlorine yields bleaching powder.
Calcium hydroxide [Ca(OH)2] yields bleaching powder when treated with chlorine.
Q -3- Name the sodium compound which is used for softening hard water.
Sodium carbonate (Washing soda) is used for softening the hard water.
Q -4- What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
When solution of sodium hydrocarbonate is heated, sodium carbonate, water and carbon dioxide gas is formed.
Q -5- Write an equation to show the reaction between Plaster of Paris and water.
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