题目

An old farmer lived with his little grandson. Every day the farmer got up early to read books.One day the grandson asked, Grandpa! I want to read books just like you, but I don't understand them. What are the advantages of reading? The grandfather said, Take this little basket to the river and bring me back a basket of water. The boy did so, but all the water leaked out before he got back to the house. The grandfather laughed and said, You'll have to walk faster next time.This time the boy ran faster, but again the basket was empty before he returned home. The boy said, See Grandpa, it's usele将含有杂质的铁屑30g与足量的稀盐酸反应（杂质不反应）生成标准状态下的氢气11.2 L（标准状态下的氢气的密度为0.0893g/L）试求铁屑中铁的质量分数．