CBSE EXAMINATION PAPER-2023

In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution 'X' the solution 'X' first turns milky and then colourless.

The option that justifies the above stated observation is that 'X' is aqueous calcium hydroxide and

The emission of brown fumes in the given experimental set-up is due to

Select washing soda from the following:

An organism which breaks down the food material outside the body and then absorbs it is

Consider the following statements about small intestine and select the one which is NOT correct:

The statement that correctly describes the characteristic(s) of a gene is:

Select from the following the correct statement about tropic movement in plants:

Select the INCORRECT match (between the plant and its vegetative part) from the following:

If four identical resistors, of resistance 8 Ω, are first connected in series so as to give an effective resistance Rₛ, and then connected in parallel so as to give an effective resistance Rₚ, then the ratio Rₛ⁄Rₚ is

1. In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have

Assertion (A): Blood clotting prevents excessive loss of blood.

Reason (R): Blood clotting is due to blood plasma and white blood cells present in the blood.

Assertion (A): The strength of the magnetic field produced at the centre of a current-carrying circular coil increases on increasing the number of turns in it.

Reason (R): The current in each circular turn has the same direction and the magnetic field due to each turn adds up.

(i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper quantity of water.

Identify 'X' and write its chemical formula.

(ii) State the difference in chemical composition between baking soda and baking powder.

Write balanced chemical equation for the reaction that occurs when:

(i) blue coloured copper sulphate crystals are heated and

(ii) Sodium hydrogen carbonate is heated during cooking.

(a) Write the role of insulin in regulating blood sugar levels in human body. Mention the disease caused due to it.

(b) How is the timing and the amount of release of insulin in the blood regulated?

Name the type of blood (oxygenated / deoxygenated) transported by each of the following mentioning the path (i.e. from one organ (which place) to another (which place)).

(i) Vena cava

(ii) Pulmonary artery

With the help of a schematic flow chart, show the breakdown of glucose in a cell to provide energy -

(i) in the presence of oxygen

(ii) in lack of oxygen

Name the part of the human excretory system where nephrons are found.

Write the structure and function of nephrons.

A narrow beam XY of white light is passing through a glass prism ABC as shown in the diagram:

Trace it on your answer sheet and show the path of the emergent beam as observed on the screen PQ.

Name the phenomenon observed and state its cause.

It is observed that the power of an eye to see nearby objects as well as far off objects diminishes with age.

(i) Give reason for the above statement.

(ii) Name the defect that is likely to arise in the eyes in such a condition.

(iii) Draw a labelled ray diagram to show the type of corrective lens used for restoring the vision of such an eye.

How do harmful chemicals get accumulated progressively at each trophic level in a food chain?

(a) Identify the reducing agent in the following reactions:
(i) 4NH₃ + 5O₂ → 4NO + 6H₂O

(ii) H₂O + F₂ → HF + HOF

(iii) Fe₂O₃ + 3CO → 2Fe + 3CO₂

(iv) 2H₂ + O₂ → 2H₂O

(b) Define a redox reaction in terms of gain or loss of oxygen.

(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases :
(i) Production of too much acid in stomach during indigestion
(ii) Stung by a honey bee / nettle leaves
(b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease ? Why?

(i) State the role of ATP in cellular respiration.

(ii) What ensures sufficient exchange of gases in plants?

(iii) State the conditions on which the direction of diffusion of gases in plant depend upon.

(a) Complete the following ray diagram to show the formation of image

(b) Mention the nature, position and size of the image formed in this case.

(c) State the sign of the image distance in this case using the Cartesian sign convention.

(i) State the rule used to find the force acting on a current carrying conductor placed in a magnetic field.

(ii) Given below are three diagrams showing entry of an electron in a magnetic field. Identify the case in which the force will be (1) maximum and (2) minimum respectively. Give reason for your answer.

(i) Draw the pattern of magnetic field lines of

(1) a current carrying solenoid

(2) a bar magnet

(ii) List two distinguishing features between the two fields.

(i) Why does a kitchen garden called an artificial ecosystem while a forest is considered to be a natural ecosystem?

(ii) While designing an artificial ecosystem at home, write any two things to be kept in mind to convert it into a self-sustaining system. Give reason to justify your answer.

(i) Construct a food chain of four trophic levels comprising the following:

Hawk, snake, plants, rat.

(ii) 20,000 J of energy was transferred by the producers to the organism of second trophic level. Calculate the amount of energy that will be transferred by organisms of the third trophic level to the organisms of the fourth trophic level.

A saturated organic compound A belongs to the homologous series of alcohols.

On heating A with concentrated sulphuric acid at 443K, it forms an unsaturated compound B with molecular mass 28 u.

The compound B on addition of one mole of hydrogen in the presence of nickel changes to a saturated hydrocarbon C.

(i) Identify A, B and C.

(ii) Write the chemical equations showing the conversion of A into B.

(iii) What happens when compound C undergoes combustion?

(iv) State one industrial application of hydrogenation reaction.

(v) Name the products formed when compound A reacts with sodium.

(i) With the help of diagram, show the formation of micelles when soap is applied on oily dirt.

(ii) Take two test tubes X and Y with 10 mL of hard water each. In test tube X add a few drops of soap solution and in test tube Y add a few drops of detergent solution. Shake both for the same period.

(1) In which test tube will the formation of foam be more? Why?

(2) In which test tube is a curdy solid formed? Why?

(a) Name the parts of a bisexual flower that are not directly involved in reproduction. 

(b) Differentiate between self pollination and cross pollination. List any two significance of pollination.

(c) What is the fate of ovules and ovary after fertilization in a flower?

(a) An electric iron consumes energy at a rate of 880 W when heating is at the maximum rate and 330 W when the heating is at the minimum. If the source voltage is 220 V, calculate the current and resistance in each case.
(b) What is heating effect of electric current ?
(c) Find an expression for the amount of heat produced when a current passes through a resistor for some time.