问题 计算题

(9分)将0.1mol的镁铝混合物溶于100mL 2 mol·L1的H2SO4中,然后再滴加1 mol·L1的NaOH溶液。请回答:

(1)若在滴加NaOH溶液的过程中,沉淀质量m随加入NaOH溶液的体积V的变化如图所示。当V1=160mL时,则金属粉末中,n(Mg)=_______mol,V2=_______mL。

(2)若在滴加NaOH溶液的过程中,欲使Mg2、Al3刚好沉淀完全,则滴入NaOH溶液的体积V (NaOH)=_______mL。

答案

(1)0.06  440   (2)400

(1)根据图像可知硫酸是过量的,当V1=160mL时,和金属反应的硫酸是0.2mol-0.16mol÷2=0.12mol,。设混合物中镁和铝的物质的量分别是x、y,则x+y=0.1mol、x+1.5y=0.12mol,解得y=0.04mol,x=0.06mol。所以和氯化镁、氯化铝反应消耗的氢氧化钠分别是0.12mol和0.12mol,而溶解氢氧化铝消耗的氢氧化钠是0.04mol,共计0.28mol,需要氢氧化钠溶液的体积是280ml,所以V2=160ml+280ml=440ml。

(2)根据(1)可知,要生成的沉淀最多,需要氢氧化钠溶液的体积是400ml。

单项选择题 A2型题
填空题

Exercising to music pumps up brain power


If music makes you smarter, and exercise helps brain function, can exercising to music really boost brainpower Some researchers said it can. Volunteers who listened to Vivaldi’s "Four Seasons" while working out on a treadmill did much better on a test of (1) ability than when they exercised without music, a team (2) Ohio State University found.
"Evidence suggests that exercise improves the (3) performance of people with coronary artery (4) ," said psychologist Charles Emery, who led the study.
"And listening to music is (5) to enhance brainpower. We wanted to put the two results together," Emery (6) in a statement.
Writing in the latest issue of the journal Heart & Lung, Emery and (7) said they studied 33 men and women taking (8) in a cardiac rehabilitation program after having bypass (9) , angioplasty or other procedures to treat clogged arteries.
The (10) said they felt better emotionally and mentally after working out (11) or without the music. But their improvement on the (12) fluency test doubled after listening to music on the treadmills.
"Exercise seems to (13) positive changes in the nervous system, and these changes may have a (14) effect on cognitive ability," Emery said.
"Listening to music may (15) cognitive function through different pathways in the brain. The combination of music (16) exercise may stimulate and increase cognitive arousal (17) helping to organize cognitive output."
Emery said he now wanted to (18) people using music of their own choice. "We used the ’Four Seasons’ because of its (19) tempo and positive effects on medical patients in previous (20) ," Emery said. "But given the range of music preferences among patients, it’s especially important to evaluate the influence of other types of music on cognitive outcomes.\