Daily Question (December 7)

Thread Content

This post was last edited by yanran88 on 2010-12-6 at 22:38. Daily question (December 7th); please hide your replies – thank you for your cooperation! 1. The mass of a substance per unit volume is called the （） of that substance. A. Specific gravity B. Density C. Weight density D. Viscosity 2. The ratio of the return flow rate to the production rate is called ( ). A. Reflux index B. Recovery ratio C. Reflux ratio D. Feed ratio 3. Which of the following statements is correct? ( ) A. Substances with the same molecular weight are the same substance. B. Different substances with the same molecular formula must be isomers. C. Different substances with the same general formula must be homologs. D. Substances with different functional groups and different molecular structures are isomers. 4. Since the flow velocity of a fluid varies at different points across its cross-section, the flow velocity is ( ) closer to the center of the pipe, and it is ( ) closer to the wall of the pipe. A. Larger, smaller B. Smaller, larger C. Smaller, smaller D. Larger, larger 5. The main factors affecting the service life of furnace tubes include carburization, ( ), and creep. A. Change in raw materials B. Change in temperature C. Change in pressure D. Bending deformation