CBSE Class 11 Chemistry Term 1 Sample Paper 2025 With Solutions:  Preparing for half-yearly exams? Don’t worry, as we have got you covered. Check this article to get CBSE Class 11 Chemistry Term 1 Sample Paper 2025 With Solutions. The sample paper is based on the latest syllabus and exam pattern. It provides students with a clear understanding of the types of questions that will be asked in the exam. Check the article to see. 

CBSE Class 11 Chemistry Half-Yearly Sample Paper 2025 With Solutions:

Students can check the sample paper below along with their answers: 

SECTION-A

1. What will be the molarity of a solution which contains 5.85 g of NaCl (s) per 500mL?

(A) 4 mol L-1

(B) 20 mol L-1

(C) 0.2 mol L-1

(D) 2 mol L-1

2. The empirical formula and molecular mass of a compound are CH2O and 180 g, respectively. What will be the molecular formula of the compound?

(A) C9H18O9

(B) CH2O

(C) C6H12O6

(D) C2H4O2

3. Which of the following conclusions could not be derived from Rutherford’s- particles scattering experiment?

(A) Most of the space in the atom is empty.

(B) The radius of the atom is about 10-1O m while that of the nucleus is 10-15 m.

(C) Electrons move in a circular path of fixed energy called orbits.

(D) Electrons and the nucleus are held together by electrostatic forces of attraction.

4. What electronic arrangement of an atom has the lowest ionisation enthalpy among the following?

(A) 1s2 2s2 2p3

(B) 1s2 2s2 2p63s1

(C) 1s2 2s2 2p6

(D) 1s2 2s2 2p5

5. The correct bond order in the following species is —————.

(A) O + < O – < O 2+

(B) O – < O + < O 2+

(C) O 2+ < O + < O –

(D) O 2+ < O – < O +

6. The enthalpy change in a reaction does not depend upon

(A) the state of reactions and products

(B) the nature of the reactants and products

(C) different intermediate steps in the reaction

(D) initial and final enthalpy of the reaction

7. If liquids A and B form an ideal solution

(A) The entropy of mixing is zero

(B) The free energy of mixing is zero

(C) The free energy as well as the entropy of mixing are zero

(D) The enthalpy of mixing is zero

8. When NH4Cl is added to NH4OH solution, the dissociation of ammonium hydroxide is reduced. It is due to:

(A) common ion effect

(B) hydrolysis

(C) oxidation

(D) reduction

9. The addition of a carbonyl compound to HCN is an example of

(A) Nucleophilic substitution

(B) Electrophilic addition

(C) Nucleophilic addition

(D) Electrophilic substitution

10. A base according to the Bronsted concept is a substance which can:

 (A) lose a pair of electrons

 (B) donate protons

 (C) gain a pair of electrons

 (D) accept protons

11. In the Chlorination of benzene, which of the following acts as an electrophile?

(a) Cl+

(b) Cl–

(c) Cl

(d) FeCl3

12. Which of the following will not undergo the Friedel-Crafts reaction readily?

(a) Toluene

(b) Xylene

(c) Cumene

(d) Nitrobenzene

Given below are two statements labelled as Assertion (A) and Reason (R)

13) Assertion: Benzoic acid is stronger than Acetic acid

Reason: - Ka for benzoic acid is 6.5 x 10-5 and for acetic acid is 1.74 x 10-5. Select the most appropriate answer from the options given below:

(a) Both A and R are true, and R is the correct explanation of A.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true.

14) Assertion (A): Simple distillation can help in separating a mixture of propan-1-ol (boiling point 97°C) and propanone (boiling point 56°C).

Reason (R): Liquids with a difference of more than 20°C in their boiling points can be separated by simple distillation.

Select the most appropriate answer from the options given below:

(a) Both A and R are true, and R is the correct explanation of A.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true.

15) Assertion: Sodium acetate on Kolbe’s electrolysis gives methane. 

Reason: Methyl free radical is formed at the cathode.

Select the most appropriate answer from the options given below:

(a) Both A and R are true, and R is the correct explanation of A.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true

16) Assertion (A): Nitration of benzene with nitric acid requires the use of concentrated sulphuric acid.

Reason (R): The mixture of concentrated sulphuric acid and concentrated nitric acid produces the Nucleophile, NO +

Select the most appropriate answer from the options given below:

(a) Both A and R are true, and R is the correct explanation of A.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true.

SECTION-B

17) At STP, what will be the volume of 3.011 x 1023 molecules of H2?

OR

Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction.

4 HCl (aq) + MnO2 (s) → 2H2O (l) + MnCl2(aq) + Cl2(g). How many grams of HCl react with 5.0 g of manganese dioxide? (Atomic mass of Mn = 55 u, Cl = 35.5)

18) Consider the following species: N3- , O2- , F– , Na+ , Mg2+ and Al3+

(a) What is common in them?

(b) Arrange them in the order of increasing ionic radii

19) Explain why the BeH2 molecule has a zero-dipole moment, although the Be-H bonds are polar.

OR

Which out of NH3 and NF3 has a higher dipole moment, and why?

20) Explain why:

(i) Electron gain enthalpy of Fluorine is less negative than that of chlorine.

(ii) Oxygen has a lower first Ionisation enthalpy than N.

21) For the reaction at 298 K, 2A + B →CDH = 400 kJ mol–1 and DS = 0.2 kJ K–1 mol–1. At what temperature will the reaction become spontaneous, considering DH and DS to be constant over the temperature range?

22) Write the IUPAC name of each of the following compounds

(i) CH2 =CHCH2CH (OH)CH3.

(ii) CH3COCH(CH3)2

23) Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids? Explain

(a) Cl3CCOOH > Cl2CHCOOH > ClCH2COOH

(b) CH3CH2COOH > (CH3)2CHCOOH > (CH3)3CCOOH

SECTION-C 

24. Calculate:

(i) Mass in grams of 5.8 mol N2O

(ii) Number of moles in 8.0 g of O2 

(iii) Molar mass of 11.2 L at STP weighs 8.5 g

25. According to de Broglie, the matter should exhibit dual behaviour, that is, both particle and wave-like properties. However, a cricket ball of mass 100 g does not move like a wave when it is thrown by a bowler at a speed of 100 km/h. Calculate the wavelength of the ball and explain why it does not show wave nature.

26. Although heat is a path function but heat absorbed by the system under certain specific conditions is independent of the path. What are those conditions? Explain.

27. How can you predict the following stages of a reaction by comparing the value of Kc and Answer any two of the following-

(i) Net reaction proceeds in the forward direction. 

(ii) Net reaction proceeds in the backwards direction.

(iii) No net reaction occurs.

28. Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine. NaClO4, NaClO3, NaCIO, KCIO2, ClO3

29. What are electrophiles and nucleophiles? Explain with examples.

30. How will you convert benzene into

(i) p – p-nitrobromobenzene

(ii) m – m-nitrochlorobenzene

SECTION D

Read the following passage and answer the questions that follow:

30. Bohr's model explained that electrons can revolve only in certain permitted orbits whose angular momentum is an integral multiple of h/2π, associated with a fixed amount of energy. The Bohr theory could successfully explain the stability of atoms and the spectrum of unielectron species. The hydrogen spectrum consists of the Lyman, Balmer, Paschen, Brackett and Pfund series. Bohr's theory could not explain the spectrum of multi-electron species, the Stark effect, the Zeeman effect, the dual nature of matter, the de Broglie equation and the Heisenberg uncertainty principle, which led to the orbital concept. Electrons were filled in orbitals according to Aufbau's principle, Hund's Rule and Pauli's exclusion principle. Each electron is identified by four quantum numbers n, l, ml and ms, of which n, l, and ml were derived from Schrodinger's wave equation. Half-filled and filled orbitals are more stable due to exchange energy and symmetrical distribution of electrons.

Answer the following questions

(i) The correct order of increasing energy of the atomic orbitals

(a) 5p<4f<6s<5d (b) 5p<6s<4f<5d (c) 4f<5p<5d<6s (d) 5p<5d<4f<6s

(ii) What is the wavelength of the photon emitted when an electron in an H-atom undergoes a transition from energy level n =4 to n = 2? (RH = 109677 cm-1 )

(iii) Write the electronic configuration of (a) Chromium, (b) Copper

31. Redox reactions are an important class of reactions which take place in our daily lives. Metals are good reducing agents because they can lose electrons easily, whereas non-metals are good oxidising agents, which can gain electrons easily. In electrolytic cells, electricity is passed to bring about a redox reaction. All rechargeable batteries act as electrolytic cells while recharging. Electrochemical cells produce electricity as a result of a redox reaction. Oxidation–reduction or redox reactions are reactions that involve the transfer of electrons between chemical species. The reaction in which a species disproportionate in two oxidation states (lower and higher) is called a disproportionation reaction. The equations for oxidation-reduction reactions must be balanced for both mass and charge, which can make them challenging to balance by inspection alone. To balance such a redox equation using the half-reaction method, the equation is first divided into two half-reactions, one representing oxidation and one representing reduction. The equations for the half-reactions are then balanced for mass and charge and, if necessary, adjusted so that the number of electrons transferred in each equation is the same. Finally, the half-reaction equations are added together, giving the balanced overall equation for the reaction.

Answer the following questions

(i) The oxidation number of Mn in KMnO4 is

(a) + 7 (b) + 5 (c) + 3 (d) – 7

(ii) Which of the following species do not show disproportionation reaction?

a) ClO– b) ClO2 – c) ClO3 – d)ClO4 –

(iii) Balance the following Redox reaction (in an Acidic medium) 

Cr2O7 2– (aq) + SO3 2– (aq) →Cr3+(aq)+ SO4 2–(aq)

SECTION-E

32. Attempt any five of the following

(a) The dipole moment of hydrogen halides decreases from HF to HI. Why?

(b) What is the covalency of NH3, NH4+ and BF4-?

(c) Which of the following compounds does not show resonance -CO2-, BO 3-, SO 2-?

(d) Discuss the shape of the following molecules based on VSEPR theory: BCl3, SiCl4

(e) Indicate the number of Sigma and π ones in HCONHCH3

(f) Which hybrid orbitals are used by the underlined carbon in the following molecules (i)CH3CHO (ii) CH3CHCH2

(g) Explain, based on the molecular orbital diagram, why O2 should be paramagnetic? 

33. Why was a change in the Bohr Model of the atom required? Due to which important development (s), the concept of movement of an electron in an orbit was replaced by the concept of probability of finding an electron in an orbital? What is the name given to the changed model of the atom?

OR

(a) The electronic energy in Bohr’s orbit is negative. How will you account for it?

(b) The ionisation energy of a hydrogen atom is 13.6 eV. What will be the energy of the first orbit of He+ and Li2+ ions?

34. (i) Give a brief description of the principles of the following techniques, taking an example in each case.

(a) Crystallisation (b) Distillation (c) Chromatography

(ii) Why does SO3 act as an electrophile?

OR

C5H11Br (A) is a given alkyl halide that reacts with ethanolic KOH to give an alkene ‘B’, which then reacts with Br2 and gives a compound ‘C’, which on dehydrobromination gives an alkyne ‘D’. When this is treated with sodium metal in liquid ammonia, 1 mole of ‘D’ gives us 1 mole of the sodium salt of ‘D’ and 1/2 mole of the hydrogen gas. Complete the hydrogenation of ‘D’, which yields a straight-chain alkane. Identify A, B, C, and D. Write the reactions involved.

Now that the question paper is available, students can also get the answers below: 

CBSE Class 11 Chemistry Term 1 Sample Paper Answer Key 2025 With Solutions

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