Science (English Medium) इयत्ता १२ - CBSE Important Questions

Write the equation involved in the following reaction:

Etard reaction

Convert the following:

Benzoic acid to Benzaldehyde.

What happens when propanone is treated with CH₃MgBr and then hydrolysed?

What happens when methanal undergoes cannizzaro reaction?

Write the chemical equations involved in the following reactions:

Carbylamine reaction

Give reasons for the following: (CH₃)₂NH is more basic than (CH₃)₃N in an aqueous solution.

Give reasons  Although –NH₂ is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline

Arrange the following in the increasing order of their pK_b values:

C₆H₅NH₂, C₂H₅NH₂, C₆H₅NHCH₃

 Arrange the following in the increasing order of their pK_b values:

C₆H₅NH₂, C₂H₅NH₂, C₆H₅NHCH₃

What is the difference between a nucleoside and nucleotide?

What is the difference between fibrous protein and globular protein ?

Write the product obtained when D-glucose reacts with H₂N − OH.

A 10% solution (by mass) of sucrose in water has freezing point of 269.15 K. Calculate the freezing point of 10% glucose in water, if freezing point of pure water is 273.15 K

Given : (Molar mass of sucrose = 342 g mol⁻¹)

(Molar mass of glucose = 180 g mol⁻¹)

After watching a programme on TV about the presence of carcinogens (cancer causing agents) Potassium bromate and Potassium iodate in bread and other bakery products, Ritu a class XII student decided to aware others about the adverse effects of these carcinogens in foods. She consultanted the school principal and requested him to instruct canteen contractor to stop selling sandwiches, pizza, burgers and other bakery products to the students. Principal took an immediate action and instructed the canteen contractor to replace the bakery products with some proteins and vitamins rich food like fruits, salads, sprouts etc. The decision was welcomed by the parents and students.

After reading the above passage, answer the following questions:

1) What are the values (at least two) displayed by Ritu?

2) Which polysaccharide component of carbohydrates is commonly present in bread?

3) Write the two types of secondary structure of proteins.

4) Give two examples of water soluble vitamins.

Give a reason for the following observations:

Amino acids behave like salts.

Write the structures of the monomers used for getting the following polymers

Melamine – formaldehyde polymer

Due to hectic and busy schedule, Mr Angad made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr Deepak, a close friend of Mr. Angad advised him to stop taking sleeping pills and suggested to change his life lifestyle by doing yoga, meditation and some physical exercise. Mr. Angad followed his friend’s advice and after few days he started feeling better.

After reading the above passage, answer the following

(i) What are the values (at least two) displayed by Mr. Deepak?

(ii) Why is it not advisable to take sleeping pills without consulting doctor?

(iii) What are tranquilisers? Give two examples.

You are Navtej/Navita, Secretary, Environment Club, Akash Public School, Agra. You, along with a group of students, went on a 3-day tour through Corbett National Park. You found how the tourists abuse the available facilities and thus endanger the environment. Write a letter in 120-150 words to the editor of a national daily highlighting the situation. Suggest ways through which the environment of the Park can be saved.

Analyse any five problems faced by Indian farmers in agriculture.

Differentiate between primary and secondary activities.