题目

      Earth Day has come and gone, but it’s a fact of daily life that 1.6 billion people around would have no electricity in their homes. Instead, most of them use wood, coal or even animal waste to heat and cook in their homes ,which also gives off greenhouse gases, causing indoor air pollution that kills 1.6million people a year, most of whom are children and women.        It’s not expected to improve much, and in Africa it’s becoming worse now. By 2030, when the Earth’s population will be likely to top 8billion, 1.3 billion people will still lack electricity. Of t氢气是未来理想的能源，天然气是人们目前已广泛使用的一种化石能源．回答下面的问题：（1）写出氢气和天然气主要成分燃烧的化学方程式：①氢气燃烧：2H2+O2 点燃 . 2H2O2H2+O2 点燃 . 2H2O；②天然气主要成分燃烧：CH4+2O2 点燃 . 2H2O+CO2CH4+2O2 点燃 . 2H2O+CO2．（2）已知氢气的热值为143×103kJ/kg，某天然气的热值为98×103kJ/kg，则完全燃烧0.5kg氢气，相当于完全燃烧0.730.73kg该天然气所放出的热量（精确到0.01）．（3）与天然气相比，用氢气作燃料除了发热量高外，请再说一条优点生成产物只有水，无任何污染（合理即可）生成产物只有水，无任何污染（合理即可）．