Acid Bases and Salts
I. Fill in the blanks
Q1: The substances that are sour in taste have _____ in them.
A1: acid
Q2: Acid turns blue litmus paper _____.
A2: red
Q3: Metal + Acid → X + Y.
X: _____
Y: _____
A3: Salt
Hydrogen
Q4: _____ is a measure of how acidic or basic a substance is.
A4: pH
Q5: Acids are of two types _____ and _____.
A5: organic, mineral
Q6: The acids which are found naturally in plants and animals are called _____.
A6: organic acids
Q7: All organic acids contain _____ and _____ atoms.
A7: carbon, hydrogen
Q8: The acids prepared from the mineral resources of the earth are called _____.
A8: mineral acids
Q9: All mineral acids contain _____ atoms but no carbon atom.
A9: hydrogen
Q10: The acidic solution that has a large quantity of water and a small quantity of acid is called _____.
A10: dilute acid
Q11: _____ acid is an important vitamin for a healthy body.
A11: Ascorbic
Q12: _____ acid is used in the production of various compounds such as PVC.
A12: Sulfuric
Q13: _____ acid is used as dyes, photographic chemicals, and pesticides.
A13: Acetic
Q14: _____ acid is used in the manufacture of rocket fuels.
A14: Nitric
Q15: The substances that are bitter in taste and have a soapy touch are known as _____.
A15: bases
Q16: Strong bases are _____ in nature while weak bases are _____ of electricity.
A16: good conductors, poor conductors
Q17: _____ chemical is made up of 3 parts of concentrated HCl and one part of concentrated HNO3.
A17: Aqua regia
Q18: _____ are special substances that show different colors in acidic and basic mediums.
A18: Indicators
Q19: The reaction in which an acid reacts with a base to form a _____ and water is called _____ reaction.
A19: salt, neutralization
Q20: Ant stings and bee stings have an _____ nature, so they are treated by applying _____ substances.
A20: acidic, basic
II. Name the following
Q1: Acid secreted by our stomach helps in the digestion of food.
A1: Hydrochloric acid (HCl)
Q2: Chemical that is known as the king of chemicals.
A2: Sulfuric acid (H2SO4)
Q3: Chemical that is used in the manufacture of nylon and synthetic dyes.
A3: Sulfuric acid (H2SO4)
Q4: Chemical name of:
• Slaked lime: Calcium hydroxide (Ca(OH)2)
• Caustic soda: Sodium hydroxide (NaOH)
• Caustic potash: Potassium hydroxide (KOH)
• Milk of magnesia: Magnesium hydroxide (Mg(OH)2)
• Baking soda: Sodium bicarbonate (NaHCO3)
• Calamine solution: Zinc carbonate (ZnCO3)
• Quicklime: Calcium oxide (CaO)
• Washing soda: Sodium carbonate (Na2CO3)
Q5: Weak base to treat indigestion.
A5: Milk of magnesia (Magnesium hydroxide)
Q6: 2 examples of salts.
A6: Sodium chloride (NaCl), Potassium nitrate (KNO3)
Q7: Synthetic indicator that gives orange color in a neutral solution.
A7: Methyl orange
Q8: Natural indicator extracted from lichens.
A8: Litmus
Q9: Chief ingredient of the white wash.
A9: Calcium hydroxide (Slaked lime)
Q10: Chemical which is injected into the skin of a person when an ant bites.
A10: Formic acid
Q11: Name the salt formed when hydrochloric acid neutralizes sodium hydroxide solution.
A11: Sodium chloride (NaCl)
III. Analogy based questions
Q1: Caustic soda: Sodium hydroxide :: _____ : Potassium hydroxide.
A1: Caustic potash
Q2: Litmus: Natural indicator :: _____ : Synthetic indicator.
A2: Phenolphthalein
Q3: _____ : Red with bases :: Phenolphthalein: Pink with bases.
A3: Turmeric
Q4: Ant sting: Acidic :: Wasp sting: _____.
A4: Alkaline
IV. Correct the underlined word
Q1: Excessive use of chemical fertilizers makes the soil basic.
A1: Excessive use of chemical fertilizers makes the soil acidic.
Q2: Ant stings and bee stings have a basic nature.
A2: Ant stings and bee stings have an acidic nature.
Q3: Basic solutions turn pink China rose indicator to Pink.
A3: Basic solutions turn pink China rose indicator to green.
Q4: Methyl Orange has yellow color in neutral solutions.
A4: Methyl Orange has orange color in neutral solutions.
V. Assertion Based Questions
Q1: Assertion: Litmus solution or Litmus Paper is used as an indicator.
Reason: Litmus is obtained from lichens and it is purple or mauve in color.
A1: a) Both A and R are true and R is the correct explanation of the Assertion.
Q2: Assertion: Neutralization reaction is accompanied by the evolution of heat.
Reason: Neutralization reaction is a reaction between an acid and a base to form salt and water.
A2: a) Both A and R are true and R is the correct explanation of the Assertion.
VI. Case Study Questions
Q1: Seema’s mother added slaked lime to the soil because the soil is _____.
A1: acidic
Q2: The possible content in the other sack was _____.
A2: c) Fertilizer
Q3: What would happen if Seema’s mother added slaked lime to the soil which was too basic?
A3: If Seema’s mother added slaked lime to the soil which was too basic, the soil would become even more basic, making it unsuitable for plant growth.
Q4: Meera is provided with three kinds of liquid solutions labeled as:
A: If no change, then it is a neutral solution.
B (Sodium hydroxide): If it turns blue litmus paper red, it is a base.
C (Hydrochloric Acid): If it turns blue litmus paper red, it is an acid.
D (Sugar solution): If no change, then it is a neutral solution.
Q5: A farmer was unhappy because of his crop yield. He discussed with an agricultural scientist and realized that the soil in his field is either too acidic or too basic. What remedies would you suggest to the farmer to neutralize the soil to get good crops?
A5:
- If the soil is too acidic, add lime (calcium carbonate) or slaked lime (calcium hydroxide).
- If the soil is too basic, add organic matter like compost or manure, or sulfur.
VII. Think and Tell
Q1: Why should factory waste be neutralized before discharging it into water bodies?
A1: Factory waste should be neutralized before discharging it into water bodies to prevent harm to aquatic life and to avoid water pollution.
Q2: Ant sting is acidic, that is why our skin burns after its stings. Can you apply soap solution to pacify burning? Give a reason.
A2: Applying a soap solution to pacify the burning from an ant sting is effective because soap is basic and neutralizes the acidic sting.
Q3: What happens when the lining of the stomach fails to protect itself from HCl secreted in the stomach?
A3: When the lining of the stomach fails to protect itself from HCl secreted in the stomach, it can lead to ulcers and damage to the stomach lining.
Q4: Why vinegar is added to packaged food items like sauces, ketchups, pickles, etc?
A4: Vinegar is added to packaged food items like sauces, ketchups, and pickles as a preservative to inhibit the growth of bacteria and fungi.
Q5: Why acid should be added to water and water is never added to an acid?
A5: Acid should be added to water and not vice versa to avoid splattering and exothermic reactions that can cause burns.
Q6: Why are acids stored in glass containers and not in metal containers?
A6: Acids are stored in glass containers because glass is resistant to corrosion by acids, unlike metals.
Q7: After carrying out a neutralization reaction, the test tube is immediately found to be somewhat hot. Explain why?
A7: The test tube becomes hot after a neutralization reaction because the reaction is exothermic and releases heat.
Q8: Why is an antacid tablet taken when we suffer from acidity?
A8: An antacid tablet is taken when we suffer from acidity to neutralize excess stomach acid and relieve discomfort.
VIII. High Order Thinking Skills Questions
Q1: Boojho, Paheli, and their friend Golu were provided with a test, each containing China rose solution which was pink in color. Boojho added 2 drops of solution A in his test tube and got a dark pink color. Paheli added 2 drops of solution B to her test tube and got green color. Golu added solution C but could not get any change in color. Suggest the possible cause for the variation in their results.
A1: The variation in the results:
- Solution A is acidic (turned China rose solution dark pink).
- Solution B is basic (turned China rose solution green).
- Solution C is neutral (no change in color).
Q2: Rohan observes the following results while doing an experiment with four solutions to identify which solution is acidic, basic, or neutral:
Solution P: Red with blue litmus, no change with red litmus.
Solution Q: Deep Red with blue litmus, no change with red litmus.
Solution R: No change with blue litmus, Blue with red litmus.
Solution S: No change with both blue and red litmus.
A2:
- Strongly acidic: Solution P (turned blue litmus red).
- Neutral: Solution S (no change in either litmus).
- Basic: Solution R (turned red litmus blue).
Q3: Ravi gets a turmeric stain on his cotton shirt while eating food. He washes it with soap. What change does he observe in the yellow stain? Give a reason. How should he remove the turmeric stain from clothes?
A3: Ravi observes the turmeric stain turning red due to soap (basic) reacting with turmeric (acidic). To remove the stain, rinse with an acidic solution like lemon juice or vinegar.
Q4: You have been provided with four test tubes. One of these test tubes contains distilled water, common salt, and the other two contain an acidic and a basic solution respectively. If you are given only blue litmus paper, how will you identify the contents of each test tube?
A4:
- Acidic solution: Blue litmus turns red.
- Basic solution: No change with blue litmus.
- Neutral solution: No change with blue litmus.
IX. Picture Based Questions
Q1: a) Identify the type of reaction shown and define it.
A1: The type of reaction shown is a neutralization reaction.
Q2: b) Why does the reaction mixture become hot when an acid and a base react?
A2: The reaction mixture becomes hot because the neutralization reaction is exothermic and releases heat.
Q3: You are provided with three test tubes A, B, and C as shown here. These test tubes contain different liquids. What will you observe when you put:
A3:
- A strip of red litmus paper in each test tube?
- Test tube A: Turns blue in basic solutions, remains red in acidic or neutral solutions.
- Test tube B: Turns blue in basic solutions, remains red in acidic or neutral solutions.
- Test tube C: Turns blue in basic solutions, remains red in acidic or neutral solutions.
- A strip of blue litmus paper in each test tube?
- Test tube A: Turns red in acidic solutions, remains blue in basic or neutral solutions.
- Test tube B: Turns red in acidic solutions, remains blue in basic or neutral solutions.
- Test tube C: Turns red in acidic solutions, remains blue in basic or neutral solutions.
- A few drops of phenolphthalein solution in each test tube?
- Test tube A: Turns pink in basic solutions, remains colorless in acidic or neutral solutions.
- Test tube B: Turns pink in basic solutions, remains colorless in acidic or neutral solutions.
- Test tube C: Turns pink in basic solutions, remains colorless in acidic or neutral solutions.