rab Questions 1. Antoine Lavoisier (1743 1794) was a brilliant French chemist wh

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rab Questions 1. Antoine Lavoisier (1743 1794) was a brilliant French chemist whose careful measurements with experiments on combustion led him to propose the Law of Conservation of Mass. The law states that matter can neither be created nor destroyed. Practically speaking, this means that the total mass of matter at the end of a chemical change is the same as at the beginning. How does the atomic theory explain the law of conservation of mass? The compound carbon monoxide, CO, is 42.9% by mass carbon and 57.1% by mass oxygen. The compound carbon dioxide, CO2, is 27.2% by mass carbon and 72.7% oxygen. Does this disprove the Law of Constant Composition? In your explanation, include calculations of mass percent to justify your answer 2. 83

Explanation / Answer

According to Dalton's atomic theory :

1. All matter is made up of atoms.

2. Atoms can neither be created nor be destroyed.

3. Atoms of the same element are identical.

4. Atoms of different elements have different properties.

5. compounds are formed by the combination of atoms of different elements in a particular ratio

6. A chemical reaction is a rearrangement of atoms.

According to the law of conservation of mass, matter can neither be created nor be destroyed or the mass of reactants before a chemical reaction is the same as the mass of the products of the reaction. According to Dalton's second law: atoms can neither be created nor be destroyed, and a chemical reaction is a rearrangement of atoms, which is the same as the law of conservation of mass. This is how Dalton's atomic theory explained the law of conservation of mass.

2. Yes, the given data disproves the law of constant composition. But it is known as the law of multiple proportions.

Here, the atomic mass of C = 12 g/mol and that of O = 16 g/mol

The molar mass of CO = 12+16 = 28 g/mol

Carbon monoxide (CO):

Now, the mass percent of C = (12/18)*100 = 42.9%

The mass of percent of O = 100-42.9 = 57.1%

Carbon dioxide (CO2):

The molar mass of CO2 = 12 + 2*16 = 44 g/mol

Now, the mass percent of C = (12/44)*100 = 27.3%

The mass of percent of O = 100-27.2 = 72.7%

Hence, it disproves the law of constant composition but proves the law of multiple proportions.

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