Chemistry 1st Year Basic Concepts MCQs

Students can check Chemistry 1st Year Basic Concepts MCQs here for the preparation of Entry Test MCQs here. In Chemistry, the first thing which we study is an Atom. The shortest/minor part of an element that takes part in a chemical reaction is an Atom. Then comes molecules, ions, and many others. Mass Spectrometry is used to determine the masses of Isotopes. There are two types of formulas to represent a substance including Empirical and Molecular Formula. Avogadro’s Number has its significance while studying the atom, molecules, and ions. Stoichiometry balances the quantities of products and reactants. The term Limiting reactant controls the number of whole reactions. So, here we are providing you the most important MCQs. You can prepare for them easily.

Chemistry 1st Year Basic Concepts MCQs

KEY POINTS

 

Question#1. The largest number of moles are present in:

• 3.6g H₂O
• 2.8g CO
• 4.8g C₂H₅OH
• 5.4g N₂O₅

Question#2. The stoichiometric calculations for a chemical reaction results in:

• Actual yield
• Theoretical yield
• Percentage yield
• Selectivity

Question#3. Which of the following not has equal number of atoms as that in 6g Molybdenum (A_r : 96)

• 3 g O₃
• 4 g SO₂
• 4 g Ca
• 5 g SO₃

Question#4. 1 gram molecule refers to:

• Amount in grams equivalent to 1 mole of an atom
• Amount in grams equivalent to  1 mole of a molecule
• Amount in grams equivalent to 1 mole of a molecule or a compound
• Amount in grams of an ionic compound

Question#5. Number of H⁺ ions when 0.1 mole of sulfuric acid is completely ionized in water:

• 4×6.022 x 10²³
• 2×6.002 x 10²³
• 1 x 6.022 x 10²³
• None of these

Question#6. 1 gram formula refers to:

• Amount in grams equivalent  to 1 mole of an atom
• Amount in grams equivalent to 1 mole of a covalent compound
• Amount in grams equivalent to 1 mole of an ionic compound
• Amount in grams equivalent to 1 mole of an ion

Question#7. How many electrons have to be removed to ionize 1.0 x 10^-6 mol of Ne atoms to Ne⁺ ions in a neon advertising tube?

• 6.02 x 10²³ / 1.0 x 10^-6
• 1.0 x 10^-6 x 6.02 x 10²³ / 20.2
• 1.0 x 10^-6 x 6.02 x 10²³
• 1.0 x 10^-6 x 6.02 x 10²³ / 9.65 x 10^-1

Question#8. One mole of SO₂ contains:

• 6.002 x 10²³ atoms of Oxygen
• 6.002 x 10²³ atoms of Sulphur
• 18.1 x 10²³ molecules of SO₂
• 4 g atoms of SO₂

Question#9. Mg reacts with HCl as per the following reactions:

Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)
Given that; Mg = 21g and HCl = 21g, the excess reactant is;

• Mg
  
• HCl
• Both are present in an equal stoichiometric amount
• None of these

Question#10. 5604 cm³ of H₂ gas at STP contains of hydrogen:

• 6.02 x 10²³
• 2.6 x 10²³
• 3.01 x 10²³
• 1.50 x 10²³

Question#11. Number of moles present in 0.6 grams of silica is (Atomic mass Si = 28, O = 16)?

• 0.01 mole
• 0.064 mole
• 0.044 mole
• 0.054 mole

Question#12. Gram atoms of hydrogen in 5.5g H_2:

• 5.50
  
• 2.25
• 5.45
• 2.20

Question#13. Mass in grams of 10 moles of aspartame (C₁₄H₁₈N₂O₅):

• 29400g
• 2940g
  
• 2850g
• 2800g

Question#14. % of the nitrogen in urea (NH₂CONH₂):

• 82.35%
• 35%
• 46.6%
• 55.56%

Question#15. One mole of potassium chlorate is thermally decomposed and excess of aluminum is burnt in the gaseous mixture. How many moles of aluminum oxide is formed? Respective equations are given as:

2KClO₃  → KCl + 3O₂                  4Al + 3O₂  → 2Al₂O₃

• 1
  
• 2
• 1.5
• 3

Question#16. In a mass spectrometer, increasing the magnetic field strength with constant electric field results in?

• Increased radius ‘r’
• Increased ionization
• No effect
• Increased ionization

Question#17. In a mass spectrometer, increasing the electric field with constant magnetic field results in:

• Increased radius ‘r’
• Increased ionization
• Decreased radius ‘r’
• None of the above

Question#18. When 0.5 moles of Al₂(SO₄)₃ are dissolved in water, the total number of particles produced?

• 1.2 x 10²³
• 3.0 x 10²³
• 1.5 x 10²⁴
• 2.5 x 10²³

Question#19. A smuggler was caught by Airport police and 24 g of diamond was recovered from him. How many atoms of carbon he was carrying?

• 6 x 10²³
• 1.8 x 10²⁴
• 1.2 x 10²⁴
• 2.4 x 10²⁴

Question#20. Which of the following contains 1 mole of the stated particle?

• Chlorine molecules in 35.5 g of chlorine gas
• Electrons in 1g of hydrogen gas
• Hydrogen ions in 1dm³ of 1 mol dm^-3 aqueous sulphuric acid
• Oxygen atoms in 22.4 dm³ of oxygen gas at STP

Question#21. During combustion analysis, which one is used for absorbing carbon dioxide?

• 50% KOH solution
• Mg (ClO₄)₂
• Silica gel and Mg (ClO₄)₂
• Silica gel

Question#22. Which one is a monoisotopic element?

• Cl
• H
• F
  
• Cd

Question#23. Molecular ions are produced in the mass spectrometer. Which type of molecular ions is more abundant?

• Negatively charged
• Positively charged
• H⁺ ions
• Equal positive and negative ions

Question#24. The height of the peak in mass spectrum shows:

• Number of isotopes
• Mass Number
• Relative abundance
• Number of protons

Question#25. The separation of different isotopes in the mass spectrometer is done on the basis of:

• Different amounts of positive change on each ion
• Different  m/e
• Different  e/m value
• Velocities of the ions

Question#26. Which of the following compounds has the highest % age of oxygen by weight?

• CH₃ – OH
• C₂H₅ – OH
• HCCOOH
• H₂O

Question#27. A compound contains 50% sulphur and 50% oxygen by mass. The empirical formula of the compound is:

• S₂O₃
• SO₃
• SO₂
  
• SO

Question#28. Equal volumes of CO and N₂ are taken in identical conditions, The correct relationship between masses of two gases is?

• CO < N₂
• N < CO₃
• CO = N₂
• All of these

Question#29. The technique that is not used to separate isotopes is:

• Thermal diffusion
• Ultracentrifuge
• Distillation
• Extraction

Question#30. Combustion analysis is performed for the determination of:

• The molar mass of the compound
• The structural formula of the substance
• The empirical formula of the compound
• Mass of halogens present in an organic compound