Laws of Chemical Combination - UNSOLVED PRACTICE SET

Q7. State the law of conservation of mass. Who proposed it?

Q8. State the law of definite proportions. How does it differ from the law of multiple proportions?

Q9. What is Gay-Lussac's law of gaseous volumes? Give one example.

Q10. A sample of water from a river in Uttarakhand and a sample of water from a well in Rajasthan are both pure H₂O. What does the law of definite proportions tell you about the ratio of hydrogen to oxygen in both samples?

Q11. Your mother makes laddoos using exactly 2 parts besan to 1 part sugar every time. If one day she accidentally uses 3 parts besan to 1 part sugar, the laddoos don't taste the same. How is this similar to the law of definite proportions in chemistry?

Q12. Carbon forms two oxides: carbon monoxide (CO) and carbon dioxide (CO₂). How does this illustrate the law of multiple proportions?

Q13. Explain the five laws of chemical combination with suitable examples for each:

(a) Law of conservation of mass

(b) Law of definite proportions

(c) Law of multiple proportions

(d) Gay-Lussac's law of gaseous volumes

(e) Avogadro's law

How did these laws contribute to the development of atomic theory?

Q14. Describe an experiment to verify the law of conservation of mass. Draw a labelled diagram of the apparatus used. What precautions must be taken during the experiment? Why is this law considered fundamental to chemistry?

Q15. Two students perform experiments with hydrogen and oxygen:

Student A combines 2 g hydrogen with 16 g oxygen to form water.

Student B combines 4 g hydrogen with 32 g oxygen to form water.

Student C tries to combine 2 g hydrogen with 20 g oxygen.

(a) Which student's experiment illustrates the law of conservation of mass? Calculate the mass of water formed.

(b) Which student's experiment illustrates the law of definite proportions? What is the fixed ratio?

(c) What happens in Student C's experiment? Is the law of conservation of mass violated? Explain.

(d) If Student D forms hydrogen peroxide (H₂O₂) instead of water, how does this illustrate the law of multiple proportions?

Q16. In an experiment, 12 g of magnesium ribbon is burnt in oxygen to form magnesium oxide. The mass of magnesium oxide formed is found to be 20 g.

(a) Calculate the mass of oxygen that combined with magnesium.

(b) Verify the law of conservation of mass for this reaction.

(c) If 24 g of magnesium is burnt, what mass of magnesium oxide would be formed?

Q17. Carbon forms two oxides: carbon monoxide (CO) and carbon dioxide (CO₂).

In CO, 12 g of carbon combines with 16 g of oxygen.

In CO₂, 12 g of carbon combines with 32 g of oxygen.

(a) State the law illustrated by this data.

(b) Verify this law by calculating the ratio of masses of oxygen that combine with a fixed mass (12 g) of carbon.

(c) If carbon forms another oxide C₃O₂ where 36 g carbon combines with 32 g oxygen, does this also follow the same law? Show your calculations.

Q18. Hydrogen and oxygen combine to form water according to the reaction: 2H₂ + O₂ → 2H₂O

(a) If 10 g of hydrogen reacts with 80 g of oxygen, calculate the mass of water formed and identify the excess reagent.

(b) According to Gay-Lussac's law, what volume ratio of hydrogen to oxygen is required? If 50 mL of hydrogen is used, what volume of oxygen is needed for complete reaction?

(c) If the experiment is performed in a closed container and the total mass before reaction is 100 g, what would be the total mass after reaction? Which law does this verify?