II.4?Quiz (Pts: 3/20): 1. Explain why some seed crystals are added in the satura
ID: 703120 • Letter: I
Question
II.4?Quiz (Pts: 3/20): 1. Explain why some seed crystals are added in the saturated solution. Is there any crystal being formed if we skip the step of adding seed crystals?2. Suggest a change in the procedure to make the crystallization process faster. Why rapid crystallization is not recommended to give good quality crystals? 3. In the part of preparation of CuSO4.5H2O, what can be the solid if there are some solid particles after the reaction time? How do you know if you use enough H2SO4? If H2SO4 is excess, what will you do deal with the remaining acid without affecting the crystallization procedure? Write chemical reactions if there are some chemical changes Be sure to answer all questions and give all explanation (especially in Cu(OH)2 and effect of CuSO4 parts). 3. In the part of preparation of CuSO4.5H2O, what can be the solid if there are some solid particles after the reaction time? How do you know if you use enough H2SO4? If H2SO4 is excess, what will you do deal with the remaining acid without affecting the crystallization procedure? Write chemical reactions if there are some chemical changes Be sure to answer all questions and give all explanation (especially in Cu(OH)2 and effect of CuSO4 parts).
(II) Sulphate Pentahydrate (CuSO45H2O) from Aqueous Solution 1. OBJECTIVES: Crystal growth of CuSO5H, from an aqueous solution by means of the temperature reduction method 2. KNOWLEDGE: Chemical properties of copper-related compounds. Method of preparing Copper salt. Basic crystallization. 3. EQUIPMENT: lasses Fume hood, various beakers with appropriate cover g (watch glasses), heating plate with magnetic rotation, graduated cylinders, pipette, thermometer (up to 80 °C),filter paper, latex gloves. Chemicals: CuO, Glucose, NH,OH, H,SO 4. PROCEDURE: I. Preparation of the saturated solution The following steps have to be performed: Choose desired temperature to start your growth. Temp at 45 °C is recommended. . On the basis of the solubility diagram of CuSO5H,O calculate the mass you need to saturate 30 ml HO at the chosen temperature. Figure 1: Solublty Diagram of CuSO,.5H,O in H.O Weigh the calculated mass of CuS.5H,O and do it in a cooking cup. Add 30 ml of hot distilled H,O to completely dissolve with a magnetic stirrer
Explanation / Answer
answer-A
this seeding is to start the crystalization because for crystalization seeding or nucleai is neccesary. In many crystallization experiments sufficiently high levels of saturation are not reached to allow this critical nucleation event to occur. If an environment can be created that favors a higher local concentration of macromolecules, the energy barrier for nucleation may be lowered. When seeds are introduced at lower levels of saturation in a crystallization experiment, nucleation may be facilitated and crystal growth initiated. The different techniques used for seeding such as streak, macro and seed bead will be described and particular emphasis will be given to the method of automated microseed matrix seeding which has proved to be an extremely powerful tool for obtaining and optimizing hits.
answer B
Seeding has become one of the most critical steps in optimizing crystallization behavior .
SECOND IS FIRST SUPERSATURATION SOLUTION THEN SEEDING THEN COOLING
ANSWER-C
Excess acid is just nutrailized by base (by using NaoH solution).