13 Acids Bases and Salts Chapter Wise Important Questions | PDF ... - Free Printable
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The provided document contains a series of questions and answers related to acids, bases, and salts. Below, I will explain the solutions for each question in detail:
---
The pH of a sample of vegetable soup was found to be 6.5. How is this soup likely to taste?
Answer: The taste will be slightly sour as it is weakly acidic.
Explanation:
- The pH scale ranges from 0 to 14.
- A pH of 7 is neutral.
- Values below 7 indicate acidity, and values above 7 indicate basicity.
- A pH of 6.5 is slightly below 7, indicating that the soup is weakly acidic.
- Weakly acidic substances often have a slightly sour taste.
---
Which bases are called alkalis? Give an example of alkalis.
Answer: Soluble bases are called alkalis, e.g., sodium hydroxide (NaOH).
Explanation:
- Alkalis are a subset of bases that are soluble in water.
- Examples of alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)₂).
- Sodium hydroxide (NaOH) is a strong base and is commonly used in industrial applications.
---
Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid, indicating the physical state of the reactants and products.
Answer:
\[
\text{Na}_2\text{CO}_3(s) + 2\text{HCl}(aq) \longrightarrow 2\text{NaCl}(aq) + \text{CO}_2(g) + \text{H}_2\text{O}(l)
\]
Explanation:
- Sodium carbonate (\(\text{Na}_2\text{CO}_3\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)), carbon dioxide gas (\(\text{CO}_2\)), and water (\(\text{H}_2\text{O}\)).
- The states of matter are indicated as follows:
- Solid (s): Sodium carbonate (\(\text{Na}_2\text{CO}_3\))
- Aqueous (aq): Hydrochloric acid (\(\text{HCl}\)) and sodium chloride (\(\text{NaCl}\))
- Gas (g): Carbon dioxide (\(\text{CO}_2\))
- Liquid (l): Water (\(\text{H}_2\text{O}\))
---
Write a balanced chemical equation for a neutralization reaction, mentioning the physical state of the reactants and products.
Answer:
\[
\text{NaOH}(aq) + \text{HCl}(aq) \longrightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)
\]
Explanation:
- Neutralization reactions occur when an acid reacts with a base to form salt and water.
- Here, sodium hydroxide (\(\text{NaOH}\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)) and water (\(\text{H}_2\text{O}\)).
- The states of matter are:
- Aqueous (aq): Sodium hydroxide (\(\text{NaOH}\)), hydrochloric acid (\(\text{HCl}\)), and sodium chloride (\(\text{NaCl}\))
- Liquid (l): Water (\(\text{H}_2\text{O}\))
---
What happens when chlorine is passed over slaked lime at 313K? Write the chemical equation of the reaction involved and state two uses of the product obtained.
Answer:
- Bleaching powder is formed.
- Chemical equation:
\[
\text{Ca(OH)}_2 + \text{Cl}_2 \xrightarrow{313\ \text{K}} \text{CaOCl}_2 + \text{H}_2\text{O}
\]
- Uses:
1. It is used as a bleaching agent in paper and textile industries.
2. It is used as a disinfectant in the purification of drinking water.
Explanation:
- Slaked lime (\(\text{Ca(OH)}_2\)) reacts with chlorine gas (\(\text{Cl}_2\)) at 313K to form calcium hypochlorite (\(\text{CaOCl}_2\)), also known as bleaching powder, and water (\(\text{H}_2\text{O}\)).
- Bleaching powder is widely used due to its oxidizing properties, which make it effective for bleaching and disinfection.
---
What would be the colour of red litmus in a solution of sodium carbonate?
Answer: The red litmus will change to blue in sodium carbonate solution.
Explanation:
- Sodium carbonate (\(\text{Na}_2\text{CO}_3\)) is a basic salt.
- Basic solutions turn red litmus paper blue.
- Therefore, red litmus paper will turn blue when dipped in a sodium carbonate solution.
---
Which gas is evolved when sodium hydrogen carbonate reacts with dilute hydrochloric acid?
Answer: Carbon dioxide gas is evolved.
Explanation:
- Sodium hydrogen carbonate (\(\text{NaHCO}_3\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)), water (\(\text{H}_2\text{O}\)), and carbon dioxide gas (\(\text{CO}_2\)).
- The reaction is:
\[
\text{NaHCO}_3(aq) + \text{HCl}(aq) \longrightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)
\]
---
Curd is not kept in copper and brass utensils. Why?
Answer: Curd and sour substances contain acids which react with brass and copper vessels to form poisonous salts which are harmful for our health.
Explanation:
- Curd and other sour substances contain acids (e.g., lactic acid).
- These acids can react with metals like copper and brass, forming toxic compounds such as copper salts.
- Copper salts are harmful if ingested, so curd should not be stored in copper or brass utensils.
---
Name the gas usually liberated when a dilute acid reacts with a metal. What happens when a burning candle is brought near this gas?
Answer:
- The gas liberated is \(\text{H}_2\) (hydrogen gas).
- When a burning candle is brought near hydrogen gas, it burns with a pop sound.
Explanation:
- Dilute acids react with active metals to produce hydrogen gas (\(\text{H}_2\)).
- Hydrogen gas is highly flammable. When a burning candle is brought near hydrogen gas, the hydrogen ignites, producing a loud "pop" sound.
---
What effect does an increase in concentration of \(\text{H}^+\)(aq.) in a solution have on the pH of the solution?
Answer: Higher the concentration, lower will be the pH of the solution.
Explanation:
- pH is defined as the negative logarithm of the hydrogen ion concentration (\([\text{H}^+]\)):
\[
\text{pH} = -\log[\text{H}^+]
\]
- As the concentration of \(\text{H}^+\) increases, the value of \(\log[\text{H}^+]\) becomes more negative, resulting in a lower pH.
- Therefore, a higher concentration of \(\text{H}^+\) leads to a lower pH, indicating increased acidity.
---
Which one of these has a higher concentration of \(\text{H}^+\) ions? 1 M HCl or 1 M CH₃COOH
Answer: 1 M HCl has a higher concentration of \(\text{H}^+\) ions.
Explanation:
- Hydrochloric acid (\(\text{HCl}\)) is a strong acid, meaning it completely dissociates in water:
\[
\text{HCl} \longrightarrow \text{H}^+ + \text{Cl}^-
\]
- Acetic acid (\(\text{CH}_3\text{COOH}\)) is a weak acid, meaning it only partially dissociates in water:
\[
\text{CH}_3\text{COOH} \rightleftharpoons \text{H}^+ + \text{CH}_3\text{COO}^-
\]
- Therefore, 1 M HCl will have a higher concentration of \(\text{H}^+\) ions compared to 1 M acetic acid.
---
Why does 1 M HCl solution have a higher concentration of \(\text{H}^+\) ions than 1 M CH₃COOH solution?
Answer: 1 M HCl has a higher concentration of \(\text{H}^+\) because it ionizes completely in aqueous solution, whereas \(\text{CH}_3\text{COOH}\) does not as it is a weak acid.
Explanation:
- Strong acids like HCl completely dissociate in water, releasing all their \(\text{H}^+\) ions.
- Weak acids like acetic acid (\(\text{CH}_3\text{COOH}\)) only partially dissociate, meaning only a fraction of the acid molecules release \(\text{H}^+\) ions.
- This results in a higher \(\text{H}^+\) concentration in the HCl solution compared to the acetic acid solution.
---
Which gas is generally liberated when a dilute solution of hydrochloric acid reacts with an active metal?
Answer: Hydrogen gas is liberated when active metal reacts with dilute hydrochloric acid.
Explanation:
- Active metals (e.g., zinc, magnesium, aluminum) react with dilute acids like hydrochloric acid to produce hydrogen gas (\(\text{H}_2\)) and a corresponding salt.
- For example, zinc reacts with hydrochloric acid as follows:
\[
\text{Zn}(s) + 2\text{HCl}(aq) \longrightarrow \text{ZnCl}_2(aq) + \text{H}_2(g)
\]
---
What is the colour of litmus in a solution of ammonium hydroxide?
Answer: Red litmus will turn blue in ammonium hydroxide.
Explanation:
- Ammonium hydroxide (\(\text{NH}_4\text{OH}\)) is a weak base.
- Bases turn red litmus paper blue.
- Therefore, red litmus paper will turn blue in an ammonium hydroxide solution.
---
Name the natural source of each of the following acids:
(i) Citric acid
(ii) Oxalic acid
(iii) Lactic acid
(iv) Tartaric acid
Answer:
- (i) Lemon and orange
- (ii) Tomatoes and Guava
- (iii) Sour milk (curd)
- (iv) Tamarind
Explanation:
- Citric acid is found naturally in citrus fruits like lemons and oranges.
- Oxalic acid is present in tomatoes and guavas.
- Lactic acid is produced by bacteria during the fermentation of milk, resulting in sour milk or curd.
- Tartaric acid is found in tamarind and grapes.
---
\boxed{\text{All questions have been answered as explained above.}}
---
Question 1:
The pH of a sample of vegetable soup was found to be 6.5. How is this soup likely to taste?
Answer: The taste will be slightly sour as it is weakly acidic.
Explanation:
- The pH scale ranges from 0 to 14.
- A pH of 7 is neutral.
- Values below 7 indicate acidity, and values above 7 indicate basicity.
- A pH of 6.5 is slightly below 7, indicating that the soup is weakly acidic.
- Weakly acidic substances often have a slightly sour taste.
---
Question 2:
Which bases are called alkalis? Give an example of alkalis.
Answer: Soluble bases are called alkalis, e.g., sodium hydroxide (NaOH).
Explanation:
- Alkalis are a subset of bases that are soluble in water.
- Examples of alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)₂).
- Sodium hydroxide (NaOH) is a strong base and is commonly used in industrial applications.
---
Question 3:
Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid, indicating the physical state of the reactants and products.
Answer:
\[
\text{Na}_2\text{CO}_3(s) + 2\text{HCl}(aq) \longrightarrow 2\text{NaCl}(aq) + \text{CO}_2(g) + \text{H}_2\text{O}(l)
\]
Explanation:
- Sodium carbonate (\(\text{Na}_2\text{CO}_3\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)), carbon dioxide gas (\(\text{CO}_2\)), and water (\(\text{H}_2\text{O}\)).
- The states of matter are indicated as follows:
- Solid (s): Sodium carbonate (\(\text{Na}_2\text{CO}_3\))
- Aqueous (aq): Hydrochloric acid (\(\text{HCl}\)) and sodium chloride (\(\text{NaCl}\))
- Gas (g): Carbon dioxide (\(\text{CO}_2\))
- Liquid (l): Water (\(\text{H}_2\text{O}\))
---
Question 4:
Write a balanced chemical equation for a neutralization reaction, mentioning the physical state of the reactants and products.
Answer:
\[
\text{NaOH}(aq) + \text{HCl}(aq) \longrightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)
\]
Explanation:
- Neutralization reactions occur when an acid reacts with a base to form salt and water.
- Here, sodium hydroxide (\(\text{NaOH}\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)) and water (\(\text{H}_2\text{O}\)).
- The states of matter are:
- Aqueous (aq): Sodium hydroxide (\(\text{NaOH}\)), hydrochloric acid (\(\text{HCl}\)), and sodium chloride (\(\text{NaCl}\))
- Liquid (l): Water (\(\text{H}_2\text{O}\))
---
Question 5:
What happens when chlorine is passed over slaked lime at 313K? Write the chemical equation of the reaction involved and state two uses of the product obtained.
Answer:
- Bleaching powder is formed.
- Chemical equation:
\[
\text{Ca(OH)}_2 + \text{Cl}_2 \xrightarrow{313\ \text{K}} \text{CaOCl}_2 + \text{H}_2\text{O}
\]
- Uses:
1. It is used as a bleaching agent in paper and textile industries.
2. It is used as a disinfectant in the purification of drinking water.
Explanation:
- Slaked lime (\(\text{Ca(OH)}_2\)) reacts with chlorine gas (\(\text{Cl}_2\)) at 313K to form calcium hypochlorite (\(\text{CaOCl}_2\)), also known as bleaching powder, and water (\(\text{H}_2\text{O}\)).
- Bleaching powder is widely used due to its oxidizing properties, which make it effective for bleaching and disinfection.
---
Question 6:
What would be the colour of red litmus in a solution of sodium carbonate?
Answer: The red litmus will change to blue in sodium carbonate solution.
Explanation:
- Sodium carbonate (\(\text{Na}_2\text{CO}_3\)) is a basic salt.
- Basic solutions turn red litmus paper blue.
- Therefore, red litmus paper will turn blue when dipped in a sodium carbonate solution.
---
Question 7:
Which gas is evolved when sodium hydrogen carbonate reacts with dilute hydrochloric acid?
Answer: Carbon dioxide gas is evolved.
Explanation:
- Sodium hydrogen carbonate (\(\text{NaHCO}_3\)) reacts with hydrochloric acid (\(\text{HCl}\)) to produce sodium chloride (\(\text{NaCl}\)), water (\(\text{H}_2\text{O}\)), and carbon dioxide gas (\(\text{CO}_2\)).
- The reaction is:
\[
\text{NaHCO}_3(aq) + \text{HCl}(aq) \longrightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)
\]
---
Question 8:
Curd is not kept in copper and brass utensils. Why?
Answer: Curd and sour substances contain acids which react with brass and copper vessels to form poisonous salts which are harmful for our health.
Explanation:
- Curd and other sour substances contain acids (e.g., lactic acid).
- These acids can react with metals like copper and brass, forming toxic compounds such as copper salts.
- Copper salts are harmful if ingested, so curd should not be stored in copper or brass utensils.
---
Question 9:
Name the gas usually liberated when a dilute acid reacts with a metal. What happens when a burning candle is brought near this gas?
Answer:
- The gas liberated is \(\text{H}_2\) (hydrogen gas).
- When a burning candle is brought near hydrogen gas, it burns with a pop sound.
Explanation:
- Dilute acids react with active metals to produce hydrogen gas (\(\text{H}_2\)).
- Hydrogen gas is highly flammable. When a burning candle is brought near hydrogen gas, the hydrogen ignites, producing a loud "pop" sound.
---
Question 10:
What effect does an increase in concentration of \(\text{H}^+\)(aq.) in a solution have on the pH of the solution?
Answer: Higher the concentration, lower will be the pH of the solution.
Explanation:
- pH is defined as the negative logarithm of the hydrogen ion concentration (\([\text{H}^+]\)):
\[
\text{pH} = -\log[\text{H}^+]
\]
- As the concentration of \(\text{H}^+\) increases, the value of \(\log[\text{H}^+]\) becomes more negative, resulting in a lower pH.
- Therefore, a higher concentration of \(\text{H}^+\) leads to a lower pH, indicating increased acidity.
---
Question 11:
Which one of these has a higher concentration of \(\text{H}^+\) ions? 1 M HCl or 1 M CH₃COOH
Answer: 1 M HCl has a higher concentration of \(\text{H}^+\) ions.
Explanation:
- Hydrochloric acid (\(\text{HCl}\)) is a strong acid, meaning it completely dissociates in water:
\[
\text{HCl} \longrightarrow \text{H}^+ + \text{Cl}^-
\]
- Acetic acid (\(\text{CH}_3\text{COOH}\)) is a weak acid, meaning it only partially dissociates in water:
\[
\text{CH}_3\text{COOH} \rightleftharpoons \text{H}^+ + \text{CH}_3\text{COO}^-
\]
- Therefore, 1 M HCl will have a higher concentration of \(\text{H}^+\) ions compared to 1 M acetic acid.
---
Question 12:
Why does 1 M HCl solution have a higher concentration of \(\text{H}^+\) ions than 1 M CH₃COOH solution?
Answer: 1 M HCl has a higher concentration of \(\text{H}^+\) because it ionizes completely in aqueous solution, whereas \(\text{CH}_3\text{COOH}\) does not as it is a weak acid.
Explanation:
- Strong acids like HCl completely dissociate in water, releasing all their \(\text{H}^+\) ions.
- Weak acids like acetic acid (\(\text{CH}_3\text{COOH}\)) only partially dissociate, meaning only a fraction of the acid molecules release \(\text{H}^+\) ions.
- This results in a higher \(\text{H}^+\) concentration in the HCl solution compared to the acetic acid solution.
---
Question 13:
Which gas is generally liberated when a dilute solution of hydrochloric acid reacts with an active metal?
Answer: Hydrogen gas is liberated when active metal reacts with dilute hydrochloric acid.
Explanation:
- Active metals (e.g., zinc, magnesium, aluminum) react with dilute acids like hydrochloric acid to produce hydrogen gas (\(\text{H}_2\)) and a corresponding salt.
- For example, zinc reacts with hydrochloric acid as follows:
\[
\text{Zn}(s) + 2\text{HCl}(aq) \longrightarrow \text{ZnCl}_2(aq) + \text{H}_2(g)
\]
---
Question 14:
What is the colour of litmus in a solution of ammonium hydroxide?
Answer: Red litmus will turn blue in ammonium hydroxide.
Explanation:
- Ammonium hydroxide (\(\text{NH}_4\text{OH}\)) is a weak base.
- Bases turn red litmus paper blue.
- Therefore, red litmus paper will turn blue in an ammonium hydroxide solution.
---
Question 15:
Name the natural source of each of the following acids:
(i) Citric acid
(ii) Oxalic acid
(iii) Lactic acid
(iv) Tartaric acid
Answer:
- (i) Lemon and orange
- (ii) Tomatoes and Guava
- (iii) Sour milk (curd)
- (iv) Tamarind
Explanation:
- Citric acid is found naturally in citrus fruits like lemons and oranges.
- Oxalic acid is present in tomatoes and guavas.
- Lactic acid is produced by bacteria during the fermentation of milk, resulting in sour milk or curd.
- Tartaric acid is found in tamarind and grapes.
---
Final Answer:
\boxed{\text{All questions have been answered as explained above.}}
Parent Tip: Review the logic above to help your child master the concept of acids bases and salts worksheet connected not connected.
