分析实验答案（Analyzing experiment answers）.doc

分析实验答案（Analyzing experiment answers） Experiment 1. Weighing exercises Thinking question: 1. why do we have to close the balance when we add weights, weights, weights and weights? Answer: the sensitivity of the balance depends to a great extent on the quality of the three agate edges. If the knife edge is not sharp or defective, it will affect the sensitivity of weighing; therefore, when the weights are added and removed, the scales must be closed so that the agate knife and the knife support are separated, so as to protect the agate blade. 2., the higher the sensitivity of the balance, whether the accuracy of weighing is higher? Answer: the higher the sensitivity of an analytical balance, the higher the accuracy of the weighing. Because it is too sensitive, it is difficult to achieve balance and is not easy to weigh. 3.. Can you use a spoon to sample in the weighing process? Why? Answer: descending weighing method, weighing process can not use small spoon sampling, because weighing parts have to be dipped in small spoon, affect weighing accuracy. 4. in the weighing process, observed the marking has been moved to 100 degrees right from the projection screen, the left or right heavy weight? A: in the weighing process, the reticle has been moved to the right of the 100 division from the projection screen, indicating that the right disk is heavy. Experiment two basic operation of titration analysis Thinking question: Can 1.HCl and NaOH standard solutions be prepared by direct preparation? Why? Answer: because the NaOH solid absorbs CO2 and moisture in the air, the concentration of concentrated HCl is uncertain, and HCl and NaOH standard solutions can not be prepared by direct method. 2. preparation of acid standard solution, why measure out HCl, with scales that take NaOH (S), instead of the pipette and analytical balance? Answer: because the pipette used for standard measure to measure different volume, balance analysis is used to accurately measure precision instrumen