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State and write the mathematical expression for Dalton’s law of partial pressure and explain it with a suitable example.

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#### Solution

**Dalton’s law of partial pressure:**

**Statement:**The total pressure of a mixture of two or more non-reactive gases is the sum of the partial pressures of the individual gases in the mixture.**Explanation:**Dalton’s law can be mathematically expressed as:

P_{Total}= P_{1}+ P_{2 }+ P_{3}…(at constant T and V)

where, P_{Total}is the total pressure of the mixture and P_{1}, P_{2}, P_{3}, … are the partial pressures of individual gases 1, 2, 3, … in the mixture.

For example, consider two non-reactive gases A and B. On mixing the two gases, the pressure exerted by individual gas A in the mixture of both the gases is called partial pressure of gas A (say P_{1}). Likewise, the partial pressure of gas B is P_{2}. According to Dalton’s law, the total pressure of the mixture of gas A and B at constant T and V will be given as:

P_{Total}= P_{1}+ P_{2}**Schematic illustration of Dalton’s law of partial pressures:**

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