Law of Definite Proportions

The law of definite proportions states that a pure chemical compound always contains the same elements in the same proportions by mass. This means that the ratio of the masses of the elements in a compound is always the same and can be expressed as a fixed and definite ratio.

Calcium Oxide Experiment

In the given experiment, 2.8 g of calcium oxide (CaO) prepared by heating limestone were found to contain 0.8 g of oxygen. This means that the mass ratio of calcium to oxygen in CaO is 2.8:0.8 or 7:2.

When one gram of oxygen was treated with calcium, 3.5 g of calcium oxide were obtained. This means that the mass ratio of calcium to oxygen in CaO is 3.5:1.

Verification of the Law of Definite Proportions

To verify the law of definite proportions, we need to calculate the mass ratio of calcium to oxygen in CaO using both sets of data.

- Using the first set of data, the mass ratio of calcium to oxygen in CaO is 7:2.
- Using the second set of data, the mass ratio of calcium to oxygen in CaO is 3.5:1.

Since the two mass ratios are different, it appears that the law of definite proportions is violated. However, this is not the case.

Explanation of the Results

The reason for the difference in the mass ratios is due to experimental error. The first set of data was obtained from the analysis of a sample of CaO, while the second set of data was obtained from a chemical reaction between calcium and oxygen.

In the first set of data, some impurities may have been present in the sample, which could have affected the mass ratio. In the second set of data, some of the calcium may have reacted with other substances present in the environment, which could have affected the mass ratio as well.

However, when the results are analyzed in a broader sense, it can be seen that both sets of data are consistent with the law of definite proportions. The mass ratio of calcium to oxygen in CaO is always a fixed and definite ratio, regardless of how the data is obtained.

Conclusion

In conclusion, the results of the experiment illustrate the law of definite proportions. Although there may be some experimental error, the mass ratio of calcium to oxygen in CaO is always a fixed and definite ratio. This law is an important principle in chemistry, as it allows us to predict the composition of chemical compounds and understand their properties.