Daltons Atomic Theory - UNSOLVED PRACTICE SET
Chapter: Atoms and Molecules | Topic: Daltons Atomic Theory
DALTONS ATOMIC THEORY - UNSOLVED PRACTICE SET
Topic: Daltons Atomic Theory
Multiple Choice Questions
Q1. According to Dalton's Atomic Theory, atoms of different elements:
- Are identical in all properties
- Differ in mass and chemical properties
- Can be created and destroyed in chemical reactions
- Are divisible into smaller particles
Q2. Which postulate of Dalton's Atomic Theory explains the Law of Conservation of Mass?
- Atoms are indivisible particles
- Atoms of the same element are identical in mass and properties
- Atoms can neither be created nor destroyed in a chemical reaction
- Atoms combine in simple whole number ratios to form compounds
Q3. The postulate "Atoms combine in simple whole number ratios to form compounds" explains:
- The Law of Conservation of Mass
- The Law of Definite Proportions
- The Law of Multiple Proportions
- Both (b) and (c)
Q4. Which of the following is NOT a postulate of Dalton's Atomic Theory?
- Matter is made up of very small particles called atoms
- Atoms can be divided into smaller subatomic particles
- Atoms of different elements differ in mass and chemical properties
- Atoms combine in simple whole number ratios to form compounds
Q5. Dalton's Atomic Theory was unable to explain:
- The Law of Conservation of Mass
- The Law of Definite Proportions
- The existence of isotopes
- The Law of Multiple Proportions
Q6. According to Dalton, the smallest particle of an element that can take part in a chemical reaction is:
- A molecule
- An atom
- An electron
- A compound
Short Answer Questions
Q7. State any four postulates of Dalton's Atomic Theory.
Q8. How does Dalton's Atomic Theory explain the Law of Conservation of Mass? Explain with a simple example.
Q9. Your teacher asks you to explain why water (H₂O) always contains hydrogen and oxygen in a fixed mass ratio of 1:8. How would you use Dalton's Atomic Theory to answer this?
Q10. Which postulate of Dalton's Atomic Theory was later found to be incorrect? Explain why, with a modern scientific discovery that disproved it.
Q11. "Dalton's Atomic Theory was a remarkable achievement for its time, but science is always evolving." Explain this statement by mentioning one limitation of Dalton's theory that was later corrected by modern atomic theory.
Q12. Draw a simple diagram showing how Dalton might have visualized the formation of water (H₂O) from hydrogen and oxygen atoms. Label the atoms clearly.
Long Answer Questions
Q13. State all the postulates of Dalton's Atomic Theory. For each postulate, identify which Law of Chemical Combination it explains. Also, mention the two main limitations of Dalton's theory that were discovered later.
Q14. A student argues: "Since Dalton said atoms are indivisible, we should stop studying subatomic particles like electrons and protons." Do you agree with this statement? Present a detailed argument explaining why Dalton's postulate about indivisible atoms was modified, and what discoveries led to this modification.
Q15. "Dalton's Atomic Theory laid the foundation for modern chemistry, but it was just the beginning of a much bigger journey." Discuss this statement by explaining: (i) how Dalton's theory unified the Laws of Chemical Combination, (ii) how the discovery of isotopes challenged one of his postulates, and (iii) why the theory remains valuable even today despite its limitations.
Numerical / Application-Based Problems
Q16. According to Dalton's Atomic Theory, atoms combine in simple whole number ratios. Consider the following compounds formed by elements X and Y:
- Compound A: 1 atom of X combines with 1 atom of Y
- Compound B: 1 atom of X combines with 2 atoms of Y
- Compound C: 2 atoms of X combine with 1 atom of Y
(a) If the mass of one atom of X is 12 u and the mass of one atom of Y is 16 u, calculate the molecular mass of each compound.
(b) Verify whether these compounds follow the Law of Multiple Proportions by calculating the mass ratios.
(c) If 24 g of X reacts completely with Y to form Compound A, how many grams of Y are required?
(d) How does this problem illustrate Dalton's postulate about simple whole number ratios?
Q17. Dalton assigned relative atomic masses based on hydrogen as 1. Today we use carbon-12 as the standard.
(a) If the atomic mass of oxygen is 16 u on the carbon-12 scale, what would it be on the hydrogen scale? (Atomic mass of H = 1 u, C = 12 u)
(b) If Dalton's scale had been adopted universally, how would chemical calculations be different today?
(c) Calculate the mass of water (H₂O) using both scales and show that the ratio of hydrogen to oxygen remains the same.
(d) Why did scientists eventually prefer carbon-12 over hydrogen as the standard?
Q18. In a classroom activity, students model Dalton's Atomic Theory using coloured balls to represent atoms of different elements.
- Red balls represent atoms of element A (atomic mass = 4 u)
- Blue balls represent atoms of element B (atomic mass = 8 u)
- Green balls represent atoms of element C (atomic mass = 12 u)
(a) Using these balls, show how a student can model the formation of a compound with formula AB₂.
(b) Calculate the molecular mass of AB₂.
(c) If a student combines 20 red balls with 40 blue balls, how many molecules of AB₂ can be formed? Will any atoms be left over?
(d) How does this activity help students understand Dalton's postulate about atoms combining in fixed ratios?