CBSE Class 12 Chemistry Previous Year Question Paper 2019 (Set-2)
This is the CBSE Class 12 Chemistry Previous Year Question Paper from the 2019 Main Exams, Set-2. The paper is divided into four sections: Section A contains five very short-answer questions carrying 1 mark each. Section B comprises seven short-answer questions worth 2 marks each. Section C includes twelve short-answer questions, each carrying 3 marks. Section D consists of three long-answer questions, each carrying 5 marks. While there is no overall choice, internal choices are provided in some questions across all sections. This board question paper is an invaluable resource for students preparing for their board examinations, offering insights into the exam pattern and question difficulty.
Quick info
| Board | CBSE |
|---|---|
| Class | 12 |
| Subject | Chemistry |
| Session | 2019 |
| Language | English |
| Type | Previous Year Question Paper |
| Exam type | Board Exam |
Paper pattern
The paper is structured into four sections (A, B, C, D) with questions carrying 1, 2, 3, and 5 marks respectively, totaling 70 marks.
Topics covered
Paper topics
- Colloidal state
- Emulsions and Gels
- Base strength in gas phase
- Conductivity of silicon doping
- Glucose and Fructose structure
- Lactose hydrolysis
Important topics
- Colloidal state
- Base strength
- Semiconductor doping
- Carbohydrate structure
- Disaccharides
PDF preview
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Question paper text
Chemistry Question Paper 2019 (Set-2)
General Instructions:
- All questions are compulsory
- Section A : Q. no. 1 to 5 are very short-answer questions and carry 1 mark each.
- Section B : Q. no. 6 to 12 are short-answer questions and carry 2 marks each.
- Section C : Q. no. 13 to 24 are also short-answer questions and carry 3 marks each.
- Section D : Q. no. 25 to 27 are long-answer questions and carry 5 marks each.
- There is no overall choice. However, an internal choice has been provided
in two questions of one mark, two questions of two marks, four questions of three marks and all the three questions of five marks weightage. You have to attempt only one of the choices in such questions.
- Use log tables if necessary. Use of calculators is not allowed.
Question 1
Why are medicines more effective in colloidal state? OR What is difference between an emulsion and a gel?
SOLUTION:
Some medicines are more effective in colloidal form because medicine in colloidal form is easily absorbed by the body tissues.
For example, Antibiotics like streptomycin in the form of the colloidal sol is injected into the body for the more effective result.
OR
Emulsion: It is a colloidal mixture in which both the dispersed phase and the dispersion medium are liquids. The two or more liquids present in the mixture are generally immiscible in nature. Example: Milk.
Gel: It is a colloid in which the dispersed phase i.e. liquid has combined with the dispersion medium i.e. solid to produce a semisolid material. Example: jellies.
Question 2
Arrange the following in increasing order of base strength in gas phase:
<math>(C_2H_5)_3N</math>, <math>C_2H_5NH_2</math>, <math>(C_2H_5)_2NH</math>
SOLUTION:
<math>C_2H_5NH_2</math>, <math>(C_2H_5)_2NH</math>, <math>(C_2H_5)_3N</math>
Question 3
Why conductivity of silicon increases on doping with phosphorus?
SOLUTION:
Phosphorus doping introduces phosphorus atoms in silicon crystal leading to change its electrical properties. Phosphorus atoms have 5 valence electrons which cause n- type doping. A phosphorus atom replaces silicon atom(having four valence electrons) in silicon crystal. Four out of five valence electrons of phosphorus take part in bonding while the fifth electron remains free. which lead to an increase in the conductivity of silicon crystal.
Question 4
What is the basic structural difference between glucose and fructose? OR Write the products obtained after hydrolysis of lactose.
SOLUTION:
Both Glucose and Fructose are hexose sugars with six carbon atoms but, Glucose is an aldohexose and Fructose is ketohexose which means the functional group present in glucose is aldehyde and the functional group in fructose is ketone.
CH<sub>2</sub>OH CHO
CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH
| CH-OH D-fructose CH<sub>2</sub>OH D-glucose CH<sub>2</sub>OH
Lactose is composed of <math>\beta</math>-D galactose and <math>\beta</math>-D glucose. Thus, on hydrolysis, it gives <math>\beta</math>-D galactose and <math>\beta</math>-D glucose.
<math>C_{12}H_{22}O_{11} + H_2O \rightarrow C_6H_{12}O_6 + C_6H_{12}O_6</math> Lactose Water D-Glucose D-Galactose
Frequently asked questions
What is this document?
This is the official CBSE Class 12 Chemistry Previous Year Question Paper from the 2019 Main Exams (Set-2).
What is the structure of the question paper?
The paper has four sections: Section A (1 mark questions), Section B (2 marks questions), Section C (3 marks questions), and Section D (5 marks questions).
Are there choices available in the questions?
Yes, internal choices are provided in some questions within each section, and all three questions in the 5-mark category offer choices.
How can solving this paper help students?
Solving this previous year question paper helps students understand the exam pattern, question types, marking scheme, and improve their time management and problem-solving skills for the board exams.
What is the total mark distribution?
The paper is designed for a total of 70 marks, with questions allocated 1, 2, 3, and 5 marks based on their section.
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