2003年10月15日，我国第一艘载人宇宙飞船“神州五号”发射获得圆满成功．发射飞船的火箭使用的燃料是偏二甲肼（C2H8N2），燃烧时发生如下反应：
C2H8N2+2X
2CO2+4H2O+3N2，则X的化学式为______． 点燃 .
由反应的化学方程式C2H8N2+2X
2CO2+4H2O+3N2，生成的2个CO2分子、4个H2O分子和3个N2分子中共含有C、O、H、N四种原子的个数依次为2、8、8、6，而反应前1个C2H8N2分子中所含有C、O、H、N四种原子的个数依次为2、0、8、2，根据化学变化前后原子种类、个数不变的原则，可判断2个X分子中共含有4个N原子和8个O原子，则物质X的化学式为N204； 点燃 .
故答案为：N204．
The pollution of the environment has become an important problem that the world has to face. Luckily, humans have realized it and we have been taking steps to deal with this problem. And many days have been appointed(指定). On March 12 every year, many Chinese people plant trees because it is China’s Tree Planting Day. It first began in 1979. Different countries made different days as Tree Planting Day. Some countries’ Tree Planting Day is the same day as World Forest Day, such as France. World Forest Day comes on March 21 every year. It was started by Spain in 1971. And the first World Forest Day was held on March 21, 1972. The purpose of World Forest Day is to encourage everyone to protect(保护) the trees because they are very important to our life. Earth Day comes on April 22 every year. The purpose of Earth Day is to encourage people all around the world to protect the environment. It was created in America in 1970. But it wasn’t until 2009, April 22 that was named Earth Day by the UN. Smoking is bad for our health. In order to stop people from smoking, April 7 was made as World No-Tobacco Day(世界无烟日) in 1987. The first World No-Tobacco Day began in 1988. But in 1989, it was made another day, on May 31 every year.
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