题干

某温度下,在一个2 L的密闭容器中,加入4 mol A和2 mol B进行如下反应:
3A(g)+2B(g)4C(s)+2D(g),反应一段时间后达到平衡,测得生成1.6 mol C,则下列说法正确的是

A:该反应的化学平衡常数表达式是

B:此时,B的平衡转化率是40%

C:增大该体系的压强,平衡向右移动,化学平衡常数增大

D:增加B,平衡向右移动,B的平衡转化率增大

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答案(点此获取答案解析)

B

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    In the frozen continent of Antarctica scientists fear an alien invasion — not from outer space, but carried in people's pockets and bags.

    Seeds and plants accidentally brought to Antarctica by tourists and scientists may introduce alien plant species which could threaten the survival of native plants in the finely balanced ecosystem.

    “The people that were carrying the most had lots and lots of seeds. They really were real threats,” said Dana Bergstrom, from the Australian Antarctic Division.

    “When we take things in through hitchhiking(搭车旅行) then we get species which are competitive. The plants and animals there are not necessarily competitive, so we'd start losing various precious biodiversity(生物多样性) on the (Antarctic) continent”, Bergstrom told Reuters.

    Amongst the alien species discovered were the Iceland Poppy, and Annual Winter Grass — all from cold climates and capable of growing in Antarctica.

    The Antarctic Peninsula, where most tourists travel, is now considered a “hot spot” on the frozen continent and the warmer the climate, the easier for seeds to grow. “The peninsula(半岛) is warming at some of the greatest rates on the planet,” said Bergstrom.

    The study, the first continent-wide assessment of invasive species in Antarctica, surveyed about 1,000 passengers during 2007-2008, the first year of the International Polar Year, an international effort to research the polar areas.

    Bergstrom said the one alien seed that had gained a foothold is Annual Winter Grass. It is a strong weed in the sub-Antarctic and is on the Antarctic island of King George. It has also made its way to the tail part of the Antarctic continent.