将0.2mol/L的醋酸(Ka=1.8×10-5)与0.2mol/L醋酸钠溶液混合,为使溶液的pH值维持在4.05,则酸和盐的
将0.2mol/L的醋酸(Ka=1.8×10-5)与0.2mol/L醋酸钠溶液混合,为使溶液的pH值维持在4.05,则酸和盐的比例应为()。
A.6:1
B.4:1
C.5:1
D.10:1
将0.2mol/L的醋酸(Ka=1.8×10-5)与0.2mol/L醋酸钠溶液混合,为使溶液的pH值维持在4.05,则酸和盐的比例应为()。
A.6:1
B.4:1
C.5:1
D.10:1
含盐量为9000mg(NaCl)/L的海水,在压力5.6MPa下反渗透脱盐。在25℃下,采用有效面积为12cm2的醋酸纤维素膜,测得水流量为0.012cm3/s,溶质浓度为450mg/L。求溶剂渗透系数、溶质渗透系数和脱盐率(已知该条件下,渗透压系数为1.8)。
某三相异步电动机,PN=30kW,UN=380V,三角形联结,IN=63A,nN=740r/min,KS=1.8,KC=6,TL=0.9TN,由SN=200kV·A的三相变压器供电。电动机起动时,要求从变压器取用的电流不得超过变压器的额定电流。
试问:
(1)能否直接起动?
(2)能否采用星形-三角形起动?
(3)能否选用KA=0.8的自耦变压器起动?
在一溶液聚合体系中,某单体浓度c(M)=0.2mol/L,某过氧化物引发剂浓度c(I)=4.0×10-3mol/L,60℃进行自由基聚合。已知kp=1.45×102L/(mol·s),kt=7.0×107L/(mol·s),f=1,引发剂半衰期t1/2=44h。求:
25℃时,用pH=4.00的标准缓冲溶液,测得电池:“玻璃电极|H+(a=Xmol·L-1)‖饱和甘汞电极”的电动势为0.814V,那么在c(HAc)=1.00×10-3mol·L-1的醋酸溶液中,此电池的电动势为多少?(=1.8×10-5,设a(H+)=[H+])
用0.10mol/L HCl标准溶液滴定0.10mol/L NaX(HX的Ka=5.0×10-10)。试问:能否准确滴定?并写出计算过程;若能准确滴定,计算化学计量点时的pH值?能用酚酞或甲基橙做指示剂吗?
考虑失业会如何影响索洛增长模型。假定产出是根据生产函数Y=Ka[(1-u<sup>*</sup>)L]1-a而生产的。式中,K为资本;L为劳动;u*为自然失业率。国民储蓄率为s,劳动力增长率为n。资本折旧率为δ。
a.把人均产出(y=Y/L)表示为人均资本(k=K/L)和自然失业率的函数。描述该经济的稳定状态。
b.假定政府政策的某些变化降低了自然失业率。描述这一变化随时间的推进如何影响产出。对产出的稳定状态的影响大于还是小于立即的影响?请解释。
Consider how unemployment would affect the Solow growth model. Suppose that output is produced according to the production function Y=Kα[(1-u<sup>*</sup>)L]1-α,where K is capital, L is the labor force, and u*is the natural rate of unemployment. The national saving rate is s, the labor force grows at rate n, and capital depreciates at rate δ.
a.Express output per worker (y=Y/L) as a function of capital per worker (k=K/L) and the natural rate of unemployment. Describe the steady state of this economy.
b.Suppose that some change in government policy reduces the natural rate of unemployment. Describe how this change affects output both immediately and over time. Is the steady-state effect on output larger or smaller than the immediate effect? Explain.
考虑失业会如何影响索洛增长模型。假定产出是根据生产函数Y=Ka[(1-u<sup>*</sup>)L]1-a而生产的。式中,K为资本;L为劳动;u<sup>*</sup>为自然失业率。国民储蓄率为s,劳动力增长率为n。资本折旧率为δ。
a.把人均产出(y=Y/L)表示为人均资本(k=K/L)和自然失业率的函数。描述该经济的稳定状态。
b.假定政府政策的某些变化降低了自然失业率。描述这一变化随时间的推进如何影响产出。对产出的稳定状态的影响大于还是小于立即的影响?请解释。
Consider how unemployment would affect the Solow growth model. Suppose that output is produced according to the production function Y=Kα[(1-u<sup>*</sup>)L]1-α,where K is capital, L is the labor force, and u<sup>*</sup> is the natural rate of unemployment. The national saving rate is s, the labor force grows at rate n, and capital depreciates at rate δ.
a.Express output per worker (y=Y/L) as a function of capital per worker (k=K/L) and the natural rate of unemployment. Describe the steady state of this economy.
b.Suppose that some change in government policy reduces the natural rate of unemployment. Describe how this change affects output both immediately and over time. Is the steady-state effect on output larger or smaller than the immediate effect? Explain.
非水滴定法测定盐酸丁卡因含量时,必须加入的试液是
A.高氯酸滴定液(0.1mol/L)
B.结晶紫指示液
C.醋酸汞试液
D.冰酸酸
E.醋酐
A.98.0mg
B.49.0mg
C.97.2mg
D.98.0%
E.97.2%
在一单级理论萃取器中,将356kg醋酸-水-异丙醚(A-B-S)三元混合液与124kg混合液接触。该混合液由20%的醋酸(质量分数,下同),78%的异丙醚和2%的水组成。萃余相质量为320kg,其中含醋酸20%,操作条件下的平衡数据见本例附图所示。试估算料液的组成及萃取相的组成。
试求管壁和醋酸之间的传热膜系数αi。