如图，杠杆处于平衡状态，O为支点，A为动力作用点，B为阻力作用点．请在图中画出阻力F2的力臂l2，以及作用在A点的最小动力F1的示意图．
读一读，连线。
①What do you like doing? ____ A.It's white and yellow.
②Do you like this pear tree? ____ B. Yes, it does.
③What colour is this flower?____ C.Yes, I do.
④Does it have long leaves? ____ D. They need water.
⑤What do the plants need?____ E. I like listening to music.
将5%的NaOH溶液逐滴加入到9.8g稀硫酸中，边加边搅拌，随着NaOH溶液的加入，溶液pH的变化如图所示．
（1）a点时，溶液中的溶质是 ____ （用化学式表示）．
（2）试计算稀硫酸中溶质的质量分数．____
