Class 10 Science

# Acids Bases and Salts

## In Text Solution

### Part 2

Question 1: How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?

Answer: We know that acid dissociates hydronium ions in aqueous solution. So, higher concentration of acid means higher concentration of hydronium ions. Due to this, the concentration of hydronium ions (H3O+) decreases when a solution of an acid is diluted.

Question 2: How is the concentration of hydroxide ions (OH) affected when excess base is dissolved in a solution of sodium hydroxide?

Answer: We know that base dissociates hydroxide ions in aqueous solution. So, higher concentration of base means higher concentration of hydroxide ions. Due to this, the concentration of hydroxide ions increases when excess base is dissolved in a solution of sodium hydroxide.

Question 3: 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?

Answer: 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 and has less concentration of hydronium ion.

Question 4: What effect does the concentration of H+(aq) ions have on the nature of the solution?

Answer: The concentration of H+ (aq) ions determines the acidic nature of solution. Hence, acidity of a solution increases with increase in concentration of H+ (aq) ions and vice versa.

Question 5: Do basic solutions also have H+(aq) ions? If yes, then why are these basic?

Answer: Yes basic solutions also have H+(aq) ions. They are basic because the concentration of hydroxide (OH) is more than that of H+(aq) ions.

Question 6: 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)?

Answer: If the soil is acidic then it should be treated with quick lime or slaked lime to neutralize it so that soil can be made suitable for cultivation.

Question 7: What is the common name of the compound CaOCl2?

Answer: Common name of CaOCl2 is bleaching powder.

Question 8: Name the substance which on treatment with chlorine yields bleaching powder.

Answer: Calcium hydroxide [Ca(OH)2] yields bleaching powder when treated with chlorine.

Question 9: Name the sodium compound which is used for softening hard water.

Answer: Sodium carbonate (Washing soda) is used for softening the hard water.

Question 10: What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

Answer: When solution of sodium hydrocarbonate is heated, sodium carbonate, water and carbon dioxide gas are formed.

2NaHCO3 ⇨ Na2CO3 + CO2 + H2O

Question 11: Write an equation to show the reaction between Plaster of Paris and water.

Answer: When water is mixed with Plaster of Paris, both of them undergo chemical reaction. This reaction leads to formation of gypsum which is hard substance. Plaster of Paris, on the other hand, is a powdery substance.

CaSO4.(0.5)H2O + (1.5)H2O ⇨ CaSO4.2H2O