问题 填空题

阿斯匹林的主要成分是乙酰水杨酸(化学式为C3H2O4),具有抑制血小板发挥作用的功能,是治疗心血管疾病的重要药物之一.

(1)乙酰水杨酸中氢、氧两种元素的质量比为        

(2)乙酰水杨酸具有酸性,若在其无色溶液中滴入紫色石蕊试液,观察到溶液呈    色.

(3)人体内的血小板有何作用?                 

答案

(1)1:32;(2)红;(3)加速血液凝固.

题目分析:(1)乙酰水杨酸中氢、氧两种元素的质量比为(1×2):(16×4)=1:32.

(2)紫色石蕊溶液遇酸性溶液变红,遇碱性溶液变蓝;由题意,乙酰水杨酸具有酸性,若在其无色溶液中滴入紫色石蕊试液,溶液呈红色.

(3)血小板能够堵塞伤口,其中还含有促进血液凝固的物质,起止血和加速凝血的作用.

点评:本题难度不大,掌握有关化学式的计算、酸的化学性质、人体内的血小板的作用等是正确解答本题的关键.

问答题

When workers become more efficient, it’s normally a good thing. But lately, it has acted as a powerful brake on job creation. And the question of whether the recent surge in productivity has run its course is the key to whether job growth is finally poised to take off.

One of the great surprises of the economic downturn that began 27 months ago is this.. Businesses are producing only 3 percent fewer goods and services than they were at the end of 2007, yet Americans are working nearly 10 percent fewer hours because of a mix of layoffs and cutbacks in the workweek.

(46) That means high-level gains in productivity--which in the long run is the key to a higher standard of living but in the short run contributes to sky-high unemployment. So long as employers can squeeze dramatically higher output from every worker, they won’t need to hire again despite the growing economy.

(47) On Friday, the Labor Department will release a closely watched March employment report expected to show the pest job growth in three years, driven by stabilization in the economy and a rebound from February snowstorms.

A p March job-growth number-at a time when the economy is growing at only a middling pace--would suggest that the productivity boom has largely run its course. (48) Regardless, the question of what caused the burst in workers’ efficiency is one of the great unanswered questions of the expansion and has huge stakes for the economy over the coming year.

"It is an episode that we’re going to--we, economists in general--are going to want to understand better and look at for a long time," Federal Reserve Chairman Ben S. Bernanke said at a hearing last week in which he described the productivity gains as "extraordinary" and acknowledged he had not foreseen them.

(49) Businesses have certainly not been investing in new equipment that might enable workers to be more efficient-capital expenditures plummeted during the recession and are rebounding slowly. (50) And the structural shifts occurring in the economy are so profound that one would expect productivity to be lower, rather than higher, as people need new training to work in parts of the economy that are growing, such as exports and the clean-energy sector.

So what’s happening As best as anyone can guess, the crisis that began in 2007 and deepened in 2008 caused both businesses and workers to panic.

(50) And the structural shifts occurring in the economy are so profound that one would expect productivity to be lower, rather than higher, as people need new training to work in parts of the economy that are growing, such as exports and the clean-energy sector.

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