.png)
10th Class Chemistry Chapter 10: Acids, Bases and Salts
Most Important Board Questions (Repeated More Than 2 Times)
Part 1: Short Question Answers
Q1: Give any two differences between Acids and Bases. / Write two characteristics of acid or base? (6 times)
Ans:
- Acids: Acid have sour taste. For example lemon juice.
- Bases: Bases have bitter taste and feel slippery for example soap.
- Acids: They turn blue litmus to red.
- Bases: They turn red litmus to blue.
Q2: Define acid and base? Give examples of each. (10 times)
Ans: Definition of Acid and Base in different concepts:
- Arrhenius Acid: Acid is a substance which dissociates in aqueous solution to give hydrogen ions ($H^+$). For example $HCl$.
- Arrhenius Base: Base is a substance which dissociates in aqueous solution to give hydroxide ions ($OH^-$). For example $NaOH$.
- Lewis Acid: Acid is a substance that can accept a pair of electrons. For example ($H^+$) or $AlCl_3$.
- Lewis Base: Base is a substance that can donate a pair of electrons. For example $NH_3$.
Q3: Write down the limitations of Arrhenius concept of Acid and Base? (24 times)
Ans:
- (i). This concept is applicable only in aqueous medium and does not explain the nature of acids and bases in non-aqueous mediums.
- (ii). It can only explain those compounds having $H^+$ and $OH^-$. It does not explain the nature of compounds like $CO_2$, $NH_3$ which are acid and base respectively.
Q4: Write down the names and formulae of any two mineral acids. OR Give names of two acids prepared by Jabir Bin Hayan. (6 times)
Ans:
- Hydrochloric acid: $HCl$
- Nitric acid: $HNO_3$
- Sulphuric acid: $H_2SO_4$
Q5: How conjugate acids and conjugate bases are formed? OR Define conjugate acid and conjugate base. (8 times)
Ans:
- Conjugate acid: A conjugate acid is a specie formed by accepting a proton by a base.
- Conjugate Base: A conjugate base is a specie formed by donating a proton by an acid.
Q6: Why does $AlCl_3$ act as Lewis acid? (5 times)
Ans: In $AlCl_3$, the central atom Aluminum (Al) has only six electrons around its valence shell. It requires two electrons to complete its outermost shell so it accepts a pair of electrons. Hence $AlCl_3$ act as Lewis acid.
Q7: Write any four uses of bases. (4 times)
Ans:
- Magnesium hydroxide: It is used to neutralize acidity in stomach.
- Calcium Hydroxide: It is used for manufacturing of bleaching powder.
- Sodium Hydroxide: It is used for manufacturing of soap.
- Potassium Hydroxide: It is used in alkaline batteries.
Q8: Write down the names of natural acids and their sources. (4 times)
Ans:
- Citric Acid: Citrus fruits (lemon, oranges)
- Lactic Acid: Sour milk
- Formic Acid: Stings of bees and ants
- Acetic Acid: Vinegar
Q9: Define hyper acidity (heart burning). (5 times)
Ans: Sometimes stomach produces too much acid. It causes stomach acidity called hyperacidity.
Q10: Write two uses of pH. (10 times)
Ans:
- (i) It is used to determine acidic or basic nature of a solution.
- (ii) It is used to prepare medicine, culture at microbiological particular concentration of $H^+$ ion.
Q11: Define pH scale. (4 times)
Ans: A scale is developed with the reference of molar concentration of $H^+$ ions that is called pH scale. It ranges from 0 to 14.
Q12: What is indicator? Give two examples. (13 times)
Ans: Indicators are organic compounds that have different colours in acidic and alkaline solutions. Litmus is a common indicator. Examples: Phenolphthalein and methyl orange.
Q13: What are salts? (13 times)
Ans: Salts are ionic compounds generally formed by the neutralization of an acid with a base e.g. Sodium chloride ($NaCl$).
Q14: How are insoluble salts prepared. (11 times)
Ans: Insoluble salts are prepared by mixing of two soluble salts. During the reaction exchange of ionic radicals takes place to produce two new salts, one of which precipitates out.
Q15: Why salt is neutral? Explain with an example. (9 times)
Ans: Salts have equal number of positive and negative charges. They are ionic compounds formed by neutralization. Example: $HCl + KOH \longrightarrow KCl + H_2O$.
Q16: Name any two acids used in Preservation of food. (5 times)
Ans: (i) Acetic acid (ii) Benzoic acid.
Q17: How can you explain that $Pb(OH)NO_3$ is a basic salt? (7 times)
Ans: It is a basic salt because it is formed by the incomplete neutralization of a polyhydroxy base by an acid.
Q18: Which salt is used to prepare plaster of Paris. (6 times)
Ans: Calcium sulphate ($CaSO_4 \cdot 2H_2O$) is used to prepare plaster of Paris.
Part 2: Long & Conceptual Questions
Q19: Define pH. What is pH of pure water? (18 times)
Ans: pH is the negative logarithm of molar concentration of the hydrogen ions. Formula: $pH = -\log[H^+]$. Pure water is neutral, thus its pH is 7.
Q20: What do you know about Double Salts? (5 times)
Ans: Double salts are formed by two normal salts when they are crystallized from a mixture of equimolar saturated solution. Example: Potash alum $K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O$.
Q21: Which kind of bond formed between Lewis Acid and Base OR Define adduct? (13 times)
Ans: The product of any Lewis acid-base reaction is a single species called an adduct. In an adduct, a coordinate covalent bond is formed.
Q22: Why $H^+$ ions act as Lewis acids? (6 times)
Ans: $H^+$ has no electron around its valence shell. It requires two electrons to complete its outermost shell, so it accepts a pair of electrons.
Q23: Why pure water is not a strong electrolyte? (8 times)
Ans: Pure water is a weak electrolyte because it ionizes very slightly into ions in a process called self-ionization. Its $K_w$ value is very low ($1.0 \times 10^{-14}$ at 25°C).
Generated for Students Academic Help - 2025
.png)
0 Comments