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Class 10 Chemistry Chapter 24 Carboxylic Acids Test 8 PDF | Punjab Board 2027 Model Papers
Grade 10 Chemistry Chapter 24 Carboxylic Acids Test 8
Prepare for the Class 10 Chemistry Chapter 24: Carboxylic Acids examination with our Class Test 8, Full Unit Test, and Chapter-Wise Test Series. These Punjab Board 2027 Model Papers are designed according to the new Chemistry syllabus issued by PECTAA Punjab. Students can use these chapter-wise chemistry tests to revise important concepts, practise textbook exercises, improve exam preparation, and assess their understanding of Carboxylic Acids. This resource is helpful for Class 10 students preparing for Punjab Board examinations in 2027.
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PAPER NO.08
CHEMISTRY
CHAPTER
WISE
WISE
Roll No.(in Figures):
(in Words):
Chapter 24:
Maximum Marks: 12
Carboxylic Acids
OBJECTIVE TYPE Time Allowed : 15 Minutes
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NOTE:Four possible answers A, B, C and D to each question are given. The choice which you think is correct, fill that circle in front of that question with Marker or Pen ink. Cutting or filling two or more circles will result in zero mark in that question.
Q1.12
1.Identify the ester functional group:
(A) –COOR
(B) –COOH
(C)
(D) –CH2–OH
2.The time required to prepare vinegar containing 15% ethanoic acid in oxidative fermentation is:
(A) 1 week(B) 2 weeks(C) Only 24 hours(D) 3 days
3.During the oxidation of ethanol by acidified KMnO4 which element is reduced?
(A) K(B) O(C) Mn(D) H
4.Which gas release when solid Na2CO3 reacts with ethanoic acid?
(A) H2(B) O2(C) CO2(D) SO2
5.Which organic acid is used as a component of food?
(A) Formic acid(B) Oxalic acid(C) Propanoic acid(D) Acetic acid
6.Ethyl acetate is used to extract:
(A) Sugar from sugarcane(B) Caffeine from coffee
(C) Oil from seeds(D) Salt from seawater
7.Which of the following acids is present in apples?
(A) Citric acid(B) Tartaric acid(C) Acetic acid(D) Malic acid
8.Acetic acid is used as a preservative in:
(A) Medicines(B) Cosmetics(C) Pickles(D) Beverages only
9.Which polymer is made by reacting a diol and a dicarboxylic acid?
(A) Polyethene(B) Polyester(C) Polystyrene(D) Polyamide
10.Which acid is present in vinegar?
(A) Citric acid(B) Malic acid(C) Tartaric acid(D) Acetic acid
11.Which compound is used as a synthetic fiber?
(A) Methyl acetate(B) Polyester(C) Resin(D) n-Amyl
12.Oleic acid is used in manufacture of:
(A) Fuels only(B) Plastics only(C) Soaps and detergents(D) Fertilizers only
Here is Subjective Part of Paper.
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Roll No.(in Figures):
(in Words):
Chapter 24:
Carboxylic Acids
Carboxylic Acids
SUBJECTIVE TYPE(PART - I)
Maximum Marks: 48
Time Allowed :1.45 Hours
Time Allowed :1.45 Hours
Q2.Write short answers to any FIVE (5) questions:(5×2=10)
(i)
What is an esterification reaction?
Ans: The reaction of a carboxylic acid with an alcohol in the presence of conc. H2SO4 (catalyst) to form an ester and water is called esterification.
RCOOH + R′OH ⇌ RCOOR′ + H2O
(ii)
What are carboxylic acids?
Ans: Organic compounds that contain the carboxyl functional group (–COOH) are called carboxylic acids. General formula: R–COOH.
(iii)
Name an oxidizing agent used to oxidize alcohols.
Ans: Acidified potassium permanganate (KMnO4) or acidified potassium dichromate (K2Cr2O7).
(iv)
What is oxidative fermentation?
Ans: The conversion of ethanol (dilute alcohol solution) into acetic acid by the oxygen of air in the presence of Acetobacter bacteria is called oxidative fermentation.
(v)
Why sufficient oxygen is provided during fermentation to prepare acetic acid from ethanol?
Ans: Oxygen is needed to oxidize ethanol to acetic acid and for the bacteria to stay active. Without enough oxygen the reaction slows down or stops.
(vi)
Why are carboxylic acids weak acids?
Ans: They ionize only partially in water, so they release few H+ ions.
(vii)
What is the role of carboxylic acids in the preparation of beverages?
Ans: Acids such as citric acid and phosphoric acid give a sour/tangy taste, enhance the flavour and help preserve the beverage.
(viii)
What is pure acetic acid also called?
Ans: Glacial acetic acid.
Q3.Write short answers to any FIVE (5) questions:(5×2=10)
(i)
Give a practical example in which an acid or an ester is used as a flavouring agent.
Ans: Citric acid is used in soft drinks and candies to give a sour flavour; ethyl butyrate (an ester) is used to give pineapple flavour in ice creams and sweets.
(ii)
How do carboxylic acids react with metals?
Ans: They react with active metals to form a salt and hydrogen gas.
2CH3COOH + Mg → (CH3COO)2Mg + H2↑
(iii)
Which carboxylic acids are very oftenly used as flavour enhancers?
Ans: Citric acid, tartaric acid, malic acid and acetic acid.
(iv)
How do carboxylic acids react with carbonates?
Ans: They react with carbonates to form a salt, water and carbon dioxide gas.
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2↑
(v)
Does ethanoic acid react with all metals?
Ans: No. It reacts only with metals above hydrogen in the reactivity series (e.g. Na, Mg, Zn). It does not react with metals such as Cu and Ag.
(vi)
Which property of acetic acid does make it suitable to act as preservative in pickle?
Ans: Its acidic nature: the acidity (low pH) stops the growth of bacteria and fungi that spoil food.
(vii)
How are carboxylic acids and esters used as solvents?
Ans: They dissolve many organic substances. For example, ethyl acetate is used as a solvent in paints, varnishes and nail polish remover.
(viii)
Write down the general formula of carboxylic acids?
Ans: R–COOH, or CnH2n+1COOH.
Q4.Write short answers to any FIVE (5) questions:(5×2=10)
(i)
Write name of citrus fruits?
Ans: Orange, lemon, lime, grapefruit and mandarin (kinnow).
(ii)
Write the role of carboxylic acids in food.
Ans: They give sour taste and flavour, act as preservatives (acetic acid in pickles) and some, like ascorbic acid (vitamin C), are nutrients.
(iii)
Write the uses of carboxylic acids and esters in synthetic fibers
Ans: A dicarboxylic acid and a diol join by repeated esterification to form polyester (Terylene), a synthetic fibre used for clothes, ropes and fishing nets.
(iv)
What are the applications of esters in daily life?
Ans: Esters are used in perfumes, artificial fruit flavours, nail polish remover, solvents for paints, and in making polyester fibres and plastics.
(v)
What is Plexiglass?
Ans: A transparent, light and strong plastic (polymethyl methacrylate) made from an ester. It is used instead of glass, e.g. in aircraft windows and signboards.
(vi)
Name the ester and its flavour in Apple, Pineapple.
Ans:
- Apple: methyl butyrate
- Pineapple: ethyl butyrate
(vii)
What are flavouring agents?
Ans: Substances added to food and drinks to give or improve their taste and smell, e.g. esters and acids like citric acid.
(viii)
What is the difference between fermentation reaction and a chemical reaction?
Ans: Fermentation is a slow reaction carried out by microorganisms or enzymes at mild temperature. An ordinary chemical reaction does not need living organisms and is usually faster, often needing heat or a catalyst.
(PART - II)
Note: Attempt any TWO questions.(2 × 9 = 18)
Q5.(a)
Explain fermentation reaction which is used to prepare acetic acid on commercial scale.
5
Ans: Acetic acid (vinegar) is made commercially by oxidative fermentation.
- Sugar solutions are first fermented to dilute ethanol.
- The ethanol solution is exposed to air in the presence of Acetobacter bacteria at about 30–35°C.
- Plenty of oxygen is supplied, because the bacteria need it to oxidize ethanol.
(b)
Describe the industrial applications of carboxylic acids and esters.
4
Ans:
- Carboxylic acids: acetic acid for vinegar, dyes, plastics and rayon; oleic and stearic acids for soaps and detergents; citric acid in food and drinks; formic acid in leather and rubber industries.
- Esters: solvents in paints, varnishes and nail polish remover; artificial flavours and perfumes; polyester fibres; plastics such as Plexiglass.
Q6.(a)
Explain oxidation of ethanol.
5
Ans: When ethanol is heated with an oxidizing agent such as acidified KMnO4 or K2Cr2O7, it is oxidized first to ethanal and then to ethanoic acid.
CH3CH2OH + 2[O] → CH3COOH + H2O
The purple colour of KMnO4 disappears (becomes colourless) because Mn is reduced (Mn7+ → Mn2+).
(b)
Describe applications of esters in daily life:
4
Ans:
- Perfumes and cosmetics, for their sweet fragrance.
- Artificial flavours in ice creams, candies and drinks (e.g. ethyl butyrate – pineapple).
- Ethyl acetate as nail polish remover and solvent for paints.
- Polyester for clothing and Plexiglass as a glass substitute.
Q7.(a)
What are flavouring agents? Which carboxylic acids are used as flavouring agents?
5
Ans: Flavouring agents are substances added to food to give or improve taste and aroma. Carboxylic acids used as flavouring agents:
- Citric acid (lemon, orange; soft drinks, candies)
- Tartaric acid (grapes; baking powder, jellies)
- Malic acid (apple; sweets)
- Acetic acid (vinegar; pickles, sauces)
(b)
Write down the reactions of carboxylic acids with metals.
4
Ans: Carboxylic acids react with active metals to form a metal salt (carboxylate) and hydrogen gas.
2CH3COOH + Mg → (CH3COO)2Mg + H2↑
2CH3COOH + Zn → (CH3COO)2Zn + H2↑
2CH3COOH + 2Na → 2CH3COONa + H2↑
Metals below hydrogen, such as Cu and Ag, do not react.
