Some Basic Concepts of Chemistry NEET Questions PDF
Some Basic Concepts of Chemistry NEET Questions PDF
Que 1. Why is the law of Gay-Lussac not obeyed if any reactant or product is not a gas?
Ans 1. If any reactant or product is a liquid, the volume occupied by a liquid is extremely small and hence, the law is not obeyed.
Que 2. If the speed of Shatabdi express is 150 miles per hour, then express its speed in SI unit.
Ans 2.
Que 3. A battery acid contains 24.5% by mass of H2SO4. What is the molality of the solution?
Ans 3.
Que 4. (i) Calculate the mass of a 2.5-gram atom of calcium. (Atomic mass of calcium is 40.)
(ii) Calculate the mass of a 1.5-gram molecule of water (H2O).
Ans 4. (i) 1 gram atom of calcium = gram atomic mass of calcium = 40 g
2.5 gram – atom of calcium = 40 × 2.5 = 100 g
(ii) Molecular mass of water (H2O) 1 × 2 + 16 = 18 u
1 gram molecule of H2O = gram molecular mass of H2O = 18 g
1.5 gram molecule of H2O = 1.8 × 1.5 = 27 g
Que 5. Define – (a) Average atomic mass (b) Molecular mass (c) Formula mass
Ans 5. (a) Average atomic mass – Atomic mass of an element is defined as the average relative mass of an atom of an element as compared to the mass of an atom of carbon -12 taken as 12.
(b) Molecular mass- it is the sum of atomic masses of the elements present in a molecule.
(c) Formula mass- it is the sum of atomic masses of the elements present in a formula unit of a compound.
Assertion – Reason Questions
Que 6. Assertion: Molecular weight of a compound is 44 if its vapour density is 22.
Reason: Vapour density × 2 = Molecular weights.
Ans 6. Both assertion and reason are true and the reason is the correct explanation of assertion.
Que 7. Assertion: Combustion of 16 g of methane gives 18 g of water.
Reason: In the combustion of methane, water is one of the products.
Ans 7. The assertion is wrong and the reason is true
Que 8. Assertion: A number 138.42 can be written as 1.3842 × 102 in scientific notation.
Reason: In scientific notation, a number is generally expressed as N × 10n, where N is a number between 1.00 … and 9.999 … and n is an exponent.
Que 9. Match the mass of elements are given in Column I with the number of moles given in Column II and mark the appropriate choice. Choose the correct codes form the options given below”
Column-I Column-II
(A) 28 g of He (p) 2 moles
(B) 46 g of Na (q) 7 moles
(C) 60 g of Ca (r) 1 mole
(D) 27 g of Al (s) 1.5 mole
(a) A – (s), B – (r), C – (q), D – (p)
(b) A – (p), B – (r), C – (q), D – (s)
(c) A – (r), B – (q), C – (p), D – (s)
(d) A – (q), B – (p), C – (s), D – (r)
Ans 9. (d) A – (q), B – (p), C – (s), D – (r)
Que 10. Give the correct order of initials T or F for the following statements. Use T if the statement is true and F if it is false.
(i) Gay-Lussac’s law of gaseous volumes is actually the law of definite proportion by volume.
(ii) Law of conservation of mass is true for physical change, but not for chemical change.
(iii) The percentage of oxygen in H2O2 is different from that in H2O. Hence, it violates the law of definite proportions.
(iv) Fixed mass of A reacts with two different masses of B (say x and y), then the ratio of x/y can be any positive integer.
(v) At STP, 5 mL of N2 and H2 have different no. of molecules.
(a) TTFTF (b) FTTFT (c) TFFTF (d) TFTTF
Ans 10. (c) TFFTF
Some Basic Concepts of Chemistry NEET Questions PDF
Que 11. How many atoms are contained in one mole of sucrose (C12H22O11)?
(a) 20 × 6.02 × 1023 atoms/mol (b) 45 × 6.02 × 1023 atoms/mol
(c) 5 × 6.02 × 1023 atoms/mol (d) None of these
Ans 11. (b) Total atoms in 1 molecule of C12H22O11 = 12 + 22 + 11 = 45
Total atoms in 1 mole of C12H22O11 = 45 × 6.02 × 1023 atoms/mol.
Que 12. The number of moles of barium carbonate which contains 1.5 moles of oxygen atoms is _____________
Ans 12. 0.5
Que 13. A mixture having 2 g of H2 and 32 g of oxygen occupies a volume of ______ _______ at NTP.
Ans 13. 44.8 L
Que 14. Percentage of nitrogen in urea (NH2CONH2) is ___________
Ans 14. 46.67
Que 15. The number of Li atoms in _____________ g. is 6.022×1024 atoms.
Ans 15. 70g
Que 16. If Avogadro number NA, is changed from 6.022 × 1023mol–1 to 6.022 × 1020mol–1, this would change
(a) The ratio of chemical species to each other in a balanced equation
(b) The ratio of elements to each other in a compound
(c) The definition of mass in units of grams
(d) The mass of one mole of carbon
Ans 16. (d)
Que 17. A mixture of gases contains H2 and O2 gases in the ratio of 1:4 (w/w). What is the molar ratio of the two gases in the mixture?
(a) 2 : 1 (b) 1 : 4
(c) 4 : 1 (d) 16 : 1
Ans 17. (c)
nH2/ nO2 = 1/ 2 / 4/32 = 32/8 = 4/1
Que 18. 1.0 g of magnesium is burnt with 0.56 g O2 in a closed vessel. Which reactant is left in excess and how much? (At. wt. Mg = 24; O = 16)
(a) Mg, 0.16 g (b) O2, 0.16 g
(c) Mg, 0.44 g (d) O2, 0.28 g
Ans 18. (a)
2Mg + O2 → 2MgO
2 × 24 g + 32 g
O2 is limiting reagent
∴ 32 g of O2 will react with, 2 × 24 of Mg
∴ 0.56 g of O2 will react with, 2 × 24 × 0.56 /32 = 0.84 g
∴ Excess of Mg = 1 – 0.84 = 0.16 g
Que 19. When 22.4 litres of H2(g) are mixed with 11.2 litres of Cl2(g), each at STP, the moles of HCl(g) formed are equal to
(a) 1 mol of HCl(g) (b) 2 mol of HCl(g)
(c) 0.5 mol of HCl(g) (d) 1.5 mol of HCl(g)
Ans 19. (a)
H2 + Cl2 → 2HCl as Cl2 is limiting reagent.
Que 20. 6.02 × 1020 molecules of urea are present in 100 mL of its solution. The concentration of solution is
(a) 0.01 M (b) 0.001 M
(c) 0.1 M (d) 0.02 M
Ans 20. (a)
Moles of urea = 6.02 × 1020 / 6.02 × 1023 = 10-3 moles
∴ Molarity = moles /Volume in ml × 1000 = 10-3 /100 × 1000 = 0.01 M
Some Basic Concepts of Chemistry NEET Questions PDF
Que 21. Mole fraction of the solute in a 1.00 molal aqueous solution is
(a) 1.7700 (b) 0.1770
(c) 0.0177 (d) 0.0344
Ans 21. (c)
χsolute = 1/ 1+ 55.55 = 0.0177
Que 22. Which has the maximum number of molecules among the following?
(a) 8 g H2 (b) 64 g SO2
(c) 44 g CO2 (d) 48 g O3
Ans 22. (a)
Number of molecules in H2 = 8/2 NA = 4 NA,
SO2 = 64/ 64 NA = NA
CO2 = 44/ 44 NA = NA,
O3 = 48/48 NA = NA
∴ Maximum number of molecules is present in 8 g H2
Que 23. The number of atoms in 0.1 mol of a triatomic gas is (NA = 6.02 × 1023mol–1)
(a) 6.026 × 1022 (b) 1.806 × 1023
(c) 3.600 × 1023 (d) 1.800 × 1022
Ans 23. (b)
Number of atoms = 3 × 0.1 × 6.022 × 1023 = 1.806 × 1023
Que 24. 10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. The amount of water produced in this reaction will be
(a) 3 mol (b) 4 mol
(c) 1 mol (d) 2 mol
Ans 24. (b)
Que 25. An organic compound contains carbon, hydrogen, and oxygen. Its elemental analysis gave C, 38.71%, and H, 9.67%. The empirical formula of the compound would be
(a) CH4 O (b) CH3 O
(c) CH2 O (d) CHO
Ans 25. (b)
Que 26. If the atomic weight of carbon and sulphur are 12 and 32 respectively, then an atom of C is …….. time lighter than an atom of S.
(a) 3/8 (b) 2/8
(c) 8/3 (d) 1/3
Ans 26. (a)
Que 27. The number of Fe atoms in 100 g Haemoglobin. If it contains 0.33% Fe. (Atomic mass of Fe = 56)
(a) 0.035 × 1023 (b) 35
(c) 3.5 × 1023 (d) 7 × 108
Ans 27. (a)
Mass of Fe = 100 × 0.33 /100 = 0.33 g
∴ Moles of Fe = 0.33/ 56 = 5.89 × 10–3 mole ∴
Number of atom of Fe = 5.89 × 10-3 × 6.022 × 1023 = 0.035 × 1023 atom
Que 28. The formula which gives the simplest whole number ratio of the atoms of various elements present in one molecule of a compound is
(a) Molecular formula (b) Empirical formula
(c) Mole formula (d) None of these
Ans 28. (b)
Que 29. The no. of atoms in 52 mol of argon is:
(a) 13 atoms (b) 3.13 × 1025 atoms
(c) 13.3 × 1025 atoms (d) None of these
Ans 29. (b)
Que 30. The density of water is 1 g/ml. The density of water in SI units is:
(a) 1 (b) 100
(c) 1000 (d) 10
Ans 30. (c)
Some Basic Concepts of Chemistry NEET Questions PDF
