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CLASS – XI Time – 1hr
MM - 40 SUBJECT – CHEMISTRY
GENERAL INSTRUCTIONS
SECTION : A CARRY 10 QUESTIONS (Q.1 TO Q.10 : 1 MARKS EACH )
SECTION : B CARRY 2 QUESTIONS ( Q.11 TO Q.12 : 2 MARKS EACH )
SECTION : C CARRY 4 QUESTIONS ( Q.13 TO Q.16 : 3 MARKS EACH)
SECTION : D CARRY CASE STUDY QUESTION NO. 17 (4 MARKS)
SECTION : E CARRY LONG QUESTION ( Q.18 TO Q.19 : 5 MARKS EACH)
SECTION A
Very Short Answer Type Questions (1 mark each): MCQs
1. Which of the following best describes the Bohr model of the atom?
a) Electrons move in fixed circular orbits around the nucleus.
b) Electrons are scattered throughout a positively charged sphere.
c) Electrons are found only in certain regions called orbitals.
d) Electrons are free to move around the nucleus in any path.
2. The principal quantum number (n) describes:
a) The shape of the orbital
b) The orientation of the orbital
c) The size of the orbital
d) The spin of the electron
3. Which of the following statements about isotopes is true?
a) Isotopes of an element have the same number of protons but different numbers of neutrons.
b) Isotopes of an element have different numbers of protons and neutrons.
c) Isotopes have the same atomic mass but different atomic numbers.
d) Isotopes have different chemical properties.
4. The molar mass of a substance is:
a) The mass of one atom of the substance
b) The mass of one molecule of the substance
c) The mass of one mole of the substance
d) The average mass of isotopes of the substance
5. The atomic number of an element represents:
a) The number of protons in the nucleus
b) The number of neutrons in the nucleus
c) The total number of protons and neutrons
d) The number of electrons in a neutral atom
6. Which of the following elements has the smallest atomic radius?
a) Hydrogen
b) Helium
c) Lithium
d) Beryllium
7. The empirical formula of a compound is the:
a) Simplest whole number ratio of atoms in the compound
b) Actual number of atoms of each element in a molecule
c) Mass ratio of the elements in the compound
d) Molecular formula divided by Avogadro's number
8. Which of the following sets of quantum numbers is not possible?
a) n = 3, l = 0, m = 0, s = +1/2
b) n = 2, l = 1, m = 0, s = +1/2
c) n = 3, l = 2, m = 3, s = +1/2
d) n = 4, l = 3, m = -2, s = -1/2
9. The empirical formula of a compound is CH₂O, and its molecular mass is 180 g/mol. What is the molecular formula of the compound?
a) CH₂O
b) C₆H₁₂O₆
c) C₂H₄O₂
d) C₃H₆O₃ These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses. (a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion. (b) If both Assertion and Reason are correct but Reason is not a correct explanation of the
Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.
Question 10.
Assertion (A): Combustion of 16 g of methane gives 18 g of water.
Reason (R): In the combustion of methane, water is one of the products.
Short Answer Type Questions-I (2 marks each)
Question 11. Calculate the mass percent of different elements present in sodium sulphate (Na2 SO4).
Question 12. Which of the following are iso-electronic species ?
Na+, K+, Mg2+, Ca2+, S2-, Ar.
Short Answer Type Questions-II (3 marks each)
Question 13. Determine the empirical formula of an oxide of Iron which has 69.9 % iron and 30.1 % dioxygen by mass.
Question 14. Calculate the amount of carbon dioxide that could be produced when
(i) 1 mole of carbon is burnt in air.
(ii) 1 mole of carbon is burnt in 16 g of dioxygen.
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.
Question 15. Calculate the energy of each of the photons which
(i) correspond to light of frequency 3 × 1015 Hz
(ii) have wavelength of 0-50 A.
Question 16. A photon of wavelength 4 × 10-7 m strikes on metal surface ; the work function of the metal being 2.13 eV. Calculate
(i) the energy of the photon, (ii) the kinetic energy of the
emission
(iii) the velocity of the photoelectron.
CASE STUDY : 4 marks
Question 17. Chemistry play an important role in human needs for food, health care products and improving life. Cis platin and taxol are used in chemotherapy, AZT (Azidothymidine) is used for AIDS. SI units are international units of measurement. Matter is classified into elements, compounds and mixtures, which can be homogeneous as well as heterogeneous. A mixture can be separated by physical methods, compounds can be separated by chemical methods only. Atomic mass is average of masses of isotopes depending upon their natural abundance. Empirical formula is calculated with the help of percentage composition of elements in a compound and molecular mass helps to calculate molecular formula. A chemical equation must be balanced so as to follow laws of chemical combination.
(a) Express 2.54 mm into S.I units.
(b) Out of milk, diamond, air, petrol which is pure substance?
(c) Balance the equation: NO2 + H2 O →HNO3 + NO
(d) What is percentage of Na in Na2CO3 ? (Na = 23u, C = 12, O = 16u)
LONG QUESTION : 5 Marks
Question 18. Using Aufbau principle, write the ground state electronic configuration of following atoms. (i)Boron (Z = 5) (ii) Neon (Z = 10), (iii) Aluminium (Z = 13) (iv) Chlorine (Z = 17), (v) Calcium (Z = 20) Question 19. In the reaction, A + B2——> AB2, identify the limiting reagent, if any, in the following mixtures
