10th Class Notes Chapter 10 Shorts Answers Questions.

▉Q1: Name three common household substance having: 

(a) pH value greater than 7 Ans: 

(i) White Wash Ca(OH)₂ 

(ii) Caustic Soda NaOH 

(iii) Milk of Magnesia Mg(OH)₂ 

▉(b) pH value less than

 7Ans: (i) Sour milk Lactic Acid 

(ii) apple Malic Acid 

(iii) Lemon Citrus 

(c) pH value equal to 7 Ans: 

(i) Table salt solution NaCl 

(ii) Water H₂O 

(iii) Calcium chloride CaCl₂ 

▉Q2: Define a Base and explain all alkalis are bases, but all bases are not alkalis? 

Ans: A species that release OH¯ in aqueous solution and accept a proton. 

Alkali: - A soluble base called alkali. It gives hydroxides ions in solutions. So, all alkalis are bases but all bases not alkalis. 

▉Q3: Define Bronsted-Lowry base and explain with an example that water is a Bronsted-Lowry base? 

Ans: According to Bronsted-Lowry concept: Proton donor species are known as acids While Protons acceptor species are known as bases. 

Example: HCl + H₂O H₃O⁺ + Cl¯ 

▉Q4: How can you justify that Bronsted-Lowry concept of acid and base is applicable to non-aqueous solutions? 

Ans: “An acid is a compound which donate a proton (H⁺)” “A base is a compound which accept a proton (H⁺)” 

So, the compounds which have H⁺ ions are also acts as acid in addition to water. Example: HCl The compound which has not OH ions is also act as base. Example: NH₃ 

▉Q5: Which kind of bond forms between Lewis acid and a base? 

Ans: A coordinate bond is formed between Lewis acid and base. In this type of bond shared pair of electrons denoted by only one atom to other. 

▉Q6: Why H⁺ ion acts as a Lewis acid? 

Ans: H is an electron deficient. It has empty orbital. It completes its valence shell with two electrons. So, it is electrophiles as: 

H H 

H + N H H N H H H 

▉Q7: Name two acids used in the manufacture of fertilizer? 

Ans: Nitric Acid (HNO₃) and Sulphuric Acid (H₂SO₄) are used in manufacture of fertilizer. 

▉Q8: Define pH? What is the pH of pure water? 

Ans: It is negative logarithm of hydrogen ion. pH = log(H⁺) 

Q9: How many times a solution of pH 1 will be stronger than that of a solution having pH 2?

 Ans: A solution of pH 1 has 10 times higher concentration of H⁺ than that of a solution of pH 2. 

▉Q10: Define the followings: 

(a) Normal salt 

Ans: A salt formed by total replacement of ionizable H⁺ ions of an acid by a positive metal ion or NH₄¯ ions. 

(b) Basic salt 

Ans: A salt formed by incomplete neutralization of poly hydroxyl base by an acid. 

▉Q11: Na₂SO₄ is a neutral salt while NaHSO₄ is an acid salt. Justify? 

Ans: Na₂SO₄ is formed by complete replacement of H⁺ ions from an acid. While NaHSO₄ is formed by partial replacement of H⁺ ions of an acid 

Example: 2NaOH + H₂SO₄ Na₂SO₄ + H₂O 

NaOH + H₂SO₄ NaHSO₄ + H₂O Q12: Give a few characteristic properties of salts? 

Ans: (i) Salts are found in crystalline form. 

(ii) They have high melting and Boiling point. 

(iii) These are neutral compounds. 

▉Q13: How are the soluble salts recovered from water? 

Ans: First saturated solution is prepared and then filtered it. Filtrate it crystallized by slow evaporation. So, soluble salts are separated by crystallization method. 

▉Q14: How are the insoluble salts prepared? 

Ans: Insoluble salts are prepared by mixing solutions of soluble salts. 

Example: AgNO₃ + NaCl AgCl + NaNO₃ 

Na₂CO₃ + CuSO₄ CuSO₃ + Na₂SO₄ Q15: Why a salt is neutral, explain with an example? 

Ans: Because salt is formed by neutralization reaction between acid and base. 

Example: NaOH + HCl NaCl + H₂O Q16: Name an acid used in the preservation of food? Ans: Benzoic acid (CH₆C₅OOH) and Acetic acid (CH₃COOH) Q17: Name the acids present in: 

(a) Vinegar Ans: Acetic acid (CH₃COOH) 

(b) Ant sting Ans: Formic acid (HCOOH) 

(c) Citrus Fruit 

Ans: ) H ―C― COOH 

(d) Sour milk H 

Ans: CH₃―CH 

COOH 

▉Q18: How can you justify that Pb(OH)NO₃ is a basic salt? 

Ans: Pb (OH)NO₃ has replaceable hydroxide ion which is a indication of basic salt. Thus hydroxide ion is 

neutralized by an acid. Such as: 

Pb(OH) NO₃ + HNO₃ Pb (NO₃)₂ + H₂O 

▉Q19: You are in a need of an acidic salt. How can you prepare it? 

Ans: Acidic salt is prepared by partial neutralization of an acid with a base. 

KOH + H₂SO₄ KHSO₄ + H₂O 

▉Q20: Which salt is used to prepare plaster of Paris? 

Ans: Calcium sulphate or gypsum (CaSO₄.2H₂O) is used to prepare plaster of Paris.