题目

    There are times when you find yourself unable to work out a problem. It is at this   28   that the way in which you use your teacher is important. With a good teacher, such times should be less   29   than with a bad one; so the worse the teacher, the more responsibility you have for your   30  ! Whatever your luck in this   31  , one thing is most significant and stays the same, whatever the quality of teaching you receive: if there is something you don't understand, you must ask, again and again if necessary, until you do understand it fully.   32   though t为从定量角度认识中和反应，小明同学自行设计并进行了下面实验：①在小烧杯中倒人8％的氢氧化钠溶液l0g，滴入2滴酚酞试剂后，溶液呈红色；②另取10％的稀盐酸逐滴滴加到氢氧化钠溶液中，边滴边振荡，随盐酸滴入，溶液颜色逐渐变浅；③在溶液红色消失瞬间，停止实验。若停止实验时，两溶液恰好反应。请分析小明实验后回答：（1）实验中酚酞试剂的作用是_________________________；（2）计算出这时共用去稀盐酸的质量是多少?(精确到0．1