问题 计算题

某容积为20L的氧气瓶装有30atm的氧气,现把氧气分装到容积为5L的小钢瓶中,使每个小钢瓶中氧气的压强为5atm。若每个小钢瓶中原有氧气压强为1atm,则共能分装多少瓶?(设分装过程中无漏气,且温度不变)

答案

解:设能够分装n个小钢瓶,则以20L氧气瓶中的氧气和n个小钢瓶中的氧气整体为研究对象,分装过程中温度不变,故遵守玻意耳定律

气体分装前后的状态如图所示,由玻意耳定律可知:

P1V1+nP2V2=P1'V1+nP2'V2,即

因为P1=30atm,P2=1atm,P1'=P2'=5atm,V1=20L,V2=5L

所以(瓶)

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单项选择题

There is no question that some "greenwashing" is going on in the corporate world. Bayernwerk, a Bavarian utility, began selling "Aqua Power " last year when Germany began to let customers choose their electricity supplier. Bayernwerk markets Aqua Power as 100 percent green, renewable, hydroelectric energy. But any customer who signs up gets power from the same mix of sources as before, hydro, gas, coal and nuclear. Nothing changes except some accounting, and there is no net benefit to the environment. There is a benefit, though, to Bayernwerk, which charges more for Aqua Power and has been swamped with orders for it.

Greenwashing takes many forms. "Companies often advertise themselves as environmentally friendly even though they might have some pretty hideous environment records," says Jill Johnson of the group Earth Day 2002. California’s PG&E, the utility that settled out of court after the real Erin Brockovich accused it of polluting groundwater, runs pro-environmental ads. But PG&E is due in court in November on charges of polluting wells in a second California town. "PG&E has a very good environmental track record," says spokesman Greg Pruett, citing recycling and waste reduction. Weyerhaeuser, the timber company, cuts old-growth trees in Canada but trumpets the 100 million tree seedlings it will plant this year.

Overall, the greening of corporate America is real and has not been as hard to achieve as some environmental activists imagined. That is especially true for greenhouse gases and climate change, the focus of Earth Day 2000. "Now there is more recognition by companies that there may be an economic advantage to reducing emissions of greenhouse gases," says Paul Portney, president of the think tank Resources for the Future. More and more companies are changing the way they heat and light their buildings and design their factories to reduce greenhouse gas emissions as well as their energy bills. (Energy-efficiency upgrades can save a company roughly $1 per square foot of office or factory space every year.) The reductions often exceed those called for in the 1997 international agreement on greenhouse warming called Kyoto Treaty, whose goal of reducing greenhouse emissions 7 percent from their 2000 levels is deemed so threatening to the economy by many oil, coal and chemical companies that the White House does not dare to submit to the Senate for ratification.

The author wrote this passage probably to show that ().

A. most companies have a good environmental track record

B. actions are truly taken by companies to protect the environment

C. the real motive of companies’ actions are self-centered

D. serious damages usually occur beneath the surface