One litre of mixture of `O_2` and `O_3` at STP was allowed to react with an excess of acidified solution of KI. The iodine liberated required 40 " mL of " `(M)/(10)` sodium thiosulphate solution for titration. What is the mass per cent of ozone in the mixture? Ultraviolet radiation of wavelength 300 nm can decompose ozone. Assuming that one photon can decompose one ozone molecule, how many photons would have been required for complete decomposition of ozone in the original mixture?

Explanation

To solve the problem step by step, we will follow the outlined approach based on the information given in the question.

### Step 1: Calculate the total number of moles of the gas mixture
At STP (Standard Temperature and Pressure), 1 mole of any ideal gas occupies 22.4 liters. Therefore, for a 1-liter mixture, we can use the ideal gas law to find the total number of moles (n) in the mixture.

Using the ideal gas law:
\[ PV = nRT \]

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