Some Basic Concepts Of Chemistry – Multiple Choice Questions

Q1. A statement which is not a part of Dalton’s atomic theory is:

1. Matter is made of atoms.
2. All atoms of a given element are identical.
3. Atoms are composed of sub-atomic particles called electron, proton and neutron.
4. Atoms of different elements have different mass and different properties.

Answer :- (2)

Q2. If 0.5 mole of BaCl₂ is mixed with 0.2 mole of Na₃PO_4, then the maximum number of moles of Ba₃(PO₄)₂ that can be formed will be:

1. 0.7
2. 0.5
3. 0.3
4. 0.1

Answer :- (3)

Q3. Which of the following is an element?

1. Air
2. Oxygen
3. Sugar
4. Urea

Answer :- (2)

Q4. Law of conservation of mass was given by:

1. Antoine Lavoisier
2. Avogadro
3. Joseph Proust
4. John Dalton

Answer :- (1)

Q5. Nitrogen monoxide reacts with oxygen according to the reaction:

2NO (g) + O₂ (g) → 2NO₂(g)If 12 moles of nitrogen monoxide reacts with 10 moles of oxygen, how many moles of NO₂ will be formed?

1. 2 moles
2. 8 moles
3. 6 moles
4. 12 moles

Answer :- (4)

Q6. If 10²¹ molecules are removed from 200 mg of CO_2, then the number of moles of CO₂ left are

1. 2.89 Χ 10^-3
2. 1.66 Χ 10^-3
3. 4.54 Χ 10^-3
4. 1.66 Χ 10^-2

Answer :- (1)

Q7. Vapour density of a gas is 22. Its molecular mass will be:

1. 33g
2. 22g
3. 44g
4. 11g

Answer :- (3)

Q8. Volume of 17g of NH₃ at N.T.P. will be:

1. 22.4 L
2. 2.24 L
3. 44.8 L
4. 4.48 L

Answer :- (1)

Q9. A compound prepared by any method contains the same elements in the fixed ratio by mass. The given statement is known as:

1. Law of multiple Proportions
2. Law of definite Proportions
3. Law of conservation of mass
4. Law of reciprocal Proportions

Answer :- (2)

Q10. One atomic mass unit (amu) is closest to the mass of:

1. One proton
2. The oxygen-16 nucleus
3. The carbon-12 nucleus
4. 6.022 x 10²³ atoms of hydrogen

Answer :- (1)

Q11. Molecular mass of glucose molecule (C₆H₁₂O₆) is:

1. 192 g
2. 172 g
3. 180 g
4. 182 g

Answer :- (3)

Q12. A compound contains 69.5% oxygen and 30.5% nitrogen and its molecular mass is 92g/mol. The formula of that compound is:

1. N₂O
2. NO₂
3. N₂O₄
4. N₂O₅

Answer :- (3)

Q13. Molar mass of F₂ is 38 g. How many atoms are present in 0.147 mole of F₂?

1. 6.02 Χ 10²³ atoms
2. 0.292 atoms
3. 8.78 Χ 10²² atoms
4. 1.76 Χ 10²³ atoms

Answer :- (4)

Q14. Atomic mass of bromine is 80 g. The mass of four moles of molecular bromine (Br₂) is:

1. 80 g
2. 320 g
3. 640 g
4. 40 g

Answer :- (3)

Q15. Number of moles of hydroxide ions in 0.3L of 0.005M solution of Ba (OH)₂ is:

1. 0.0075
2. 0.003
3. 0.0015
4. 0.0050

Answer :- (4)

Q16. Normality is defined as:

1. Number of moles of solute per litre of solution
2. Number of gram equivalents of solute per litre of solution
3. Number of moles of solute per 1000g of solvent
4. Amount of solute present in 100g of solution

Answer :- (2)

Q17. The empirical formula of an organic gas containing carbon and hydrogen is CH₂. The mass of 1 litre of this organic gas is exactly equal to that of 1 litre of N₂. Therefore, the molecular formula of organic compound is:

1. C₂H₄
2. C₃H₆
3. C₆H₁₂
4. C₄H₈

Answer :- (1)

Q18. In a ‘limiting reagent’ problem, is it okay to ignore coefficients in the equation?

1. Yes
2. No
3. If one product is formed in the reaction
4. Sometimes

Answer :- (2)

Q19. Which of the following has more number of atoms?

1. 1 mole of Oxygen gas
2. 1 mole of Ozone gas
3. 1 mole of Neon gas
4. 1 mole of Carbon monoxide gas

Answer :- (1)

Q20. The number of significant figures in 3256 is:

1. 2
2. 3
3. 4
4. 5

Answer :- (3)

Q21. The empirical formula of an acid CH₂O₂ is:

1. CH₂O
2. CH₂O₂
3. C₂H₄O₂
4. C₃H₆O₄

Answer :- (2)

Q22. The number of base SI units is:

1. 2
2. 7
3. 6
4. 5

Answer :- (2)

Q23. According to the Avogadro’s law, equal volumes of gases at the same temperature and pressure should contain:

1. Equal number of molecules
2. Same kinetic energy
3. Same potential energy
4. Same molartity

Answer :- (1)

Q24. 100mL of gaseous hydrogen combines with 50mL of gaseous oxygen to give 100mL of water vapours. This can be explained on the basis of:

1. Law of multiple proportions
2. Avogadro law
3. Gay Lussac’s law
4. Law of definite proportions

Answer :- (4)

Q25. How many moles of NaCl should be dissolved in 100 mL of water to get 0.2 M solution?

1. 0.1
2. 0.2
3. 0.02
4. 0.01

Answer :- (3)

Q26. Which of the following is a compound?

1. Sulphur
2. Air
3. Water
4. Gold

Answer :- (2)

Q27. Which of the following is the empirical formula for the compound iron(II) carbonate?

1. Fe(CO₃)₂
2. FeCO₃
3. Fe₂CO₃
4. Fe₂(CO₃)₂

Answer :- (2)

Q28. According to Avogadro’s law at the same temperature and pressure:

1. Equal volumes of gases contain equal number of molecules.
2. Matter can neither be created nor destroyed.
3. Matter consists of indivisible atoms.
4. Compounds are formed when atoms of different elements combine in a fixed ratio.

Answer :- (1)

Q29. The multiple 10⁻⁶ has the prefix:

1. mega
2. micro
3. milli
4. centi

Answer :- (1)

Q30. The mass of one mole of NaOH will be( At. mass of Na =23, O = 16, H =1)

1. 23
2. 80
3. 40
4. 16

Answer :- (3)

Q31. Which of the following is an element?

1. Copper metal
2. HCl
3. Sugar solution
4. Brass

Answer :- (1)

Q32. Empirical formula of an organic compound is CH and its molecular mass is 78g/mol. What is its molecular formula?

1. C₂H₂
2. C₂H₄
3. C₆H₆
4. C₂H₆

Answer :- (3)

Q33. The number of significant figures in 3.1205 are:

1. 5
2. 6
3. 3
4. 7

Answer :- (1)

Q34. Two different atoms A and B combine together to form AB. What will be AB?

1. Ion
2. Element
3. Atom
4. Molecule

Answer :- (4)

Q35. The reagent that is used up first in a chemical reaction is called:

1. Smallest reagent
2. Excess reagent
3. Limiting reagent
4. Fastest reagent

Answer :- (3)

Q36. The prefix used for 10^-18 is:

1. kilo
2. atto
3. centi
4. deci

Answer :- (2)

Q37. The atomic mass of an element is usually fractional because:

1. Elements contain impurities
2. Elements are mixture of allotropes
3. Elements are mixture of isotopes
4. Elements are mixture of isobars

Answer :- (3)

Q38. Law of definite proportions is given by:

1. Antoine Lavoisier
2. Avogadro
3. Joseph Proust
4. John Dalton

Answer :- (3)

Q39. Atomic mass of Cl is 35.5 g. Calculate the mass of 4.50 moles of chlorine gas, Cl₂.

1. 6.34 g
2. 319.5 g
3. 4.5 g
4. 160 g

Answer :- (2)

Q40. If 2 moles of H₂ and O₂ are available for the reaction, identify the limiting reagent for the reaction,

2H₂ + O₂ → 2H₂O

1. H₂
2. O₂
3. H₂O
4. Both H₂ and O₂

Answer :- (1)