题目

Have you ever know anyone who suffered from arthritis(关节炎)? Many people who suffer from the disease use cortisone(可的松)to keep their arthritis under control. Cortisone is cheap and easily available now. but because it once had to be made form animals, cortisone cost so much –up to 50 dollars a pill---that only the rich could afford it. Then a brilliant chemist named Percy Lavon Julian figured out how to make cortisone from an unlikely source: soybeans. Percy Julian was born in Montgomery, Alabama, in 1898, a time when most African-American children had no chance of getting a由氢气和氧气反应生成1mol水蒸气放热241.8kJ，写出该反应的热化学方程式：___________________________                       _______。