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Class 10 Chemistry Chapter 23 Test 5 PDF Download | Monohydroxy Alkanes | Punjab Board 2027
Grade 10 Chemistry Chapter 23 Monohydroxy Alkanes or Alcohols Test 5
Prepare for your exams with the Class 10 Chemistry Chapter 23 Class Test 5, covering Monohydroxy Alkanes or Alcohols (Topics 23.1 to 23.2) from the textbook. This chapter-wise test is part of the Punjab Board 2027 Model Papers, prepared according to the new syllabus issued by PECTAA Punjab. Students can use this Class 10 Chemistry test to revise important concepts, assess their preparation, and practise for upcoming board examinations. Explore our Chapter Wise Test Series for effective exam preparation and download the test PDF when available.
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Chapter Wise Class Test
Test No.5
Chapter-23
Monohydroxy Alkanes or Alcohols
1.Which one of following is monohydroxy alkanes?
(a) Methane(b) Alcohols(c) Propanone(d) Ethanone
Answer: (b) Alcohols
2.Fermentation must be carried out in the absence of:
(a) water(b) oxygen(c) Heat(d) Sugar
Answer: (b) oxygen – fermentation is anaerobic.
3.Example of fermentation is:
(a) Rusting of iron(b) Preparation of yogurt(c) Electrolysis of water(d) Burning of Fuel
Answer: (b) Preparation of yogurt
4.Ethanol concentration in the fermentation mixture usually does not exceed.
(a) 10%(b) 12%(c) 14%(d) 15%
Answer: (c) 14% – above this the yeast is killed (please verify with your textbook key).
5.Hydration of ethene is an example of which type of reaction?
(a) Substitution(b) Elimination(c) addition(d) Oxidation
Answer: (c) addition – water adds across the C=C double bond.
6.Alcohols can be used as fuels because they are:
(a) Non flammable(b) Flammable(c) Non Acidic(d) Toxic
Answer: (b) Flammable
7.Heat energy evolve by combustion of propanol is:
(a) 726 KJ/mol(b) 1367 KJ/mol(c) 2017 KJ/mol(d) 2676 KJ/mol
Answer: (c) 2017 KJ/mol
8.During combustion of alcohol which bond is break:
(a) C = O(b) O – H(c) C – H(d) C – C
Answer: (c) C – H – C–H, C–C and O–H bonds of the alcohol are broken (the C=O bond is formed, not broken). The paper has several possible bonds here, so please verify with your textbook key.
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Chapter Wise Class Test
Test No.5
Chapter-23
Monohydroxy Alkanes or Alcohols
2.Write short answers to any six (6) questions.[6 × 2 = 12]
- (i)Define monohydroxy alkane.Monohydroxy alkanes (alcohols) are compounds obtained by replacing one hydrogen atom of an alkane with one hydroxyl (–OH) group. General formula: CnH2n+1OH. Example: CH3CH2OH.
- (ii)What is Fermentation? Give example.Fermentation is the slow decomposition of organic compounds such as sugar and starch by the enzymes of micro-organisms (yeast), giving ethanol and carbon dioxide.
C6H12O6 Zymase 2C2H5OH + 2CO2 - (iii)Write the any critical condition of Fermentation process.Absence of air (oxygen). In the presence of oxygen the ethanol is oxidised to ethanoic acid (vinegar). The temperature must also be kept at about 35°C.
- (iv)Why hydration of ethene is an important industrial process?It is a fast, continuous process that gives pure ethanol on a large scale. Ethanol is needed as a solvent, fuel and raw material for many chemicals.
- (v)Write any two comparison of hydration of ethene and fermentation process?
- Hydration is fast and continuous; fermentation is slow and takes days.
- Hydration gives pure ethanol from non-renewable ethene; fermentation gives dilute, impure ethanol from renewable sugar.
- (vi)Write any two advantages of alcohols used as full.
- Burn cleanly with less pollution (no sulphur oxides and little smoke).
- Renewable, since they are made from plants, and they can be blended with petrol.
- (vii)At which temperature enzymes present in yeast get inactive?Above about 45°C the enzymes of yeast are destroyed (denatured) and fermentation stops.
- (viii)Why oxygen excluded when the fermentation reaction is carried out?If oxygen is present, the ethanol formed is oxidised to ethanoic acid (vinegar) by bacteria, so the yield of ethanol is lost.
- (ix)Why does butanol evolve a highter amount of heat than propanol when burn in oxygen.Butanol has one more CH2 group (more carbon and hydrogen atoms), so on burning it forms more CO2 and H2O molecules, with more strong C=O and O–H bonds. Each extra CH2 gives about 650 kJ/mol more heat (propanol 2017, butanol 2676 kJ/mol).
Note: Attempt any one question.[5 × 1 = 5]
3.
Describe the preparation of ethanol by fermentation process.
A dilute sugar solution (molasses) is mixed with yeast and kept at about 35°C, away from air, for several days.
Invertase converts sucrose to glucose and fructose:
C12H22O11 + H2O Invertase C6H12O6 + C6H12O6
Zymase then converts glucose to ethanol:
C6H12O6 Zymase 2C2H5OH + 2CO2
When ethanol reaches about 14%, the yeast stops working. The ethanol is separated by fractional distillation (about 95% pure, rectified spirit).
Invertase converts sucrose to glucose and fructose:
C12H22O11 + H2O Invertase C6H12O6 + C6H12O6
Zymase then converts glucose to ethanol:
C6H12O6 Zymase 2C2H5OH + 2CO2
When ethanol reaches about 14%, the yeast stops working. The ethanol is separated by fractional distillation (about 95% pure, rectified spirit).
4.
Write a note on Hydration of Ethene or Ethylene.
Hydration is the addition of water (steam) to ethene to form ethanol. Ethene and steam are passed over a phosphoric acid (H3PO4) catalyst at about 300°C and 60–70 atm.
CH2=CH2 + H2O H3PO4 CH3CH2OH
The reaction is reversible, so only a small part reacts in one pass; the unreacted ethene is recycled. It is a fast, continuous process that gives pure ethanol, but it uses ethene from petroleum, a non-renewable source.
CH2=CH2 + H2O H3PO4 CH3CH2OH
The reaction is reversible, so only a small part reacts in one pass; the unreacted ethene is recycled. It is a fast, continuous process that gives pure ethanol, but it uses ethene from petroleum, a non-renewable source.
