Dalton's Law of Partial Pressure states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas. However, it is important to note that this law is only applicable under certain conditions, and there are exceptions where it may not hold true. In the given mixture of gases: H2, N2, H2O2, O2, N2, CO, and Cl2, Dalton's Law of Partial Pressure may not be applicable due to the following reasons:

1. Reactive Gases: Dalton's Law assumes that the gases in the mixture are non-reacting. However, H2O2, CO, and Cl2 are reactive gases that can undergo chemical reactions under certain conditions. The presence of reactive gases can result in the formation of new compounds or changes in the gas mixture's composition, making the application of Dalton's Law invalid.

2. Non-Ideal Behavior: Dalton's Law assumes that the gases in the mixture behave ideally, meaning that there are no intermolecular forces or deviations from ideal gas behavior. However, some gases, such as CO and Cl2, may exhibit non-ideal behavior due to intermolecular attractions or repulsions. These deviations from ideal behavior can affect the individual gas pressures and make the application of Dalton's Law inaccurate.

3. Varied Molecular Weights: Dalton's Law assumes that all gases have the same molecular weight. However, in the given mixture, H2, N2, O2, and CO have different molecular weights. This difference in molecular weights can result in variations in the behavior and properties of the gases, making the application of Dalton's Law less accurate.

4. Presence of Water Vapor: Dalton's Law assumes that the gases are dry, meaning that there is no presence of water vapor. However, in the given mixture, H2O2 is present, which can introduce water vapor into the gas mixture. The presence of water vapor can lead to changes in the gas mixture's properties and behavior, making the application of Dalton's Law invalid.

In conclusion, Dalton's Law of Partial Pressure may not be applicable to the given mixture of gases due to the presence of reactive gases, non-ideal behavior, varied molecular weights, and the potential introduction of water vapor. It is important to consider these factors when determining the applicability of Dalton's Law in a specific gas mixture.