题目

As Paige watched the other kids playing football in her local park she longed to join in. But at nearly nine stone （1stone equals 6.35 kilograms）, the 11-year-old was too big to enjoy her favorite sport, she was well on her way to being another overweight member of her family. Mandy, her mum was 17th 10 lb and Anne, her grandma 15th 10 lb. Mandy, 39, and Anne, 67, both have a sweet tooth and share a love of all things stodgy. Recent figures show that two-thirds of kids will be dangerously fat by 2050, and overweight kids often become obese adults and live shorter lives as they are at high 黑白复印机用的墨粉中常添加Fe3O4粉末，Fe3O4是由Fe2+、Fe3+和O2﹣按1：2：4的个数比构成的．如图是氧化沉淀法生产复印用Fe3O4粉末的流程简图．已知第④步反应中各元素化合价保持不变． （1）Fe3O4粉末在复印机的电磁场作用下能使墨粉形成字迹或图案，这不仅利用了Fe3O4有磁性，还利用了Fe3O4是　色． （2）第②步加入试剂X，生成Fe（OH）2的反应方程式为　． （3）在第③步反应中要控制通入O2的量，以使生成的Fe（OH）2和Fe（OH）3的质量比等于　　，才能确保最终生成Fe3O4，操作Y的名称为　．