问题 选择题

下列常见的化学反应中,属于复分解反应的是(  )

A.Zn与稀H2SO4反应

B.甲烷燃烧

C.煅烧石灰石

D.NaOH溶液与稀盐酸反应

答案

复分解反应一般发生在金属氧化物和酸、非金属氧化物和碱、酸和碱、酸和盐,碱和盐、盐和盐之间.

A、Zn与稀H2SO4反应,生成硫酸锌和氢气,反应为单质与化合物生成单质与化合物的置换反应;故A不正确;

B、甲烷燃烧,甲烷与氧气反应生成二氧化碳和水,反应中有氧气这种单质参加,不符合复分解反应的特点;故B不正确;

C、石灰石的主要成分为碳酸钙,煅烧石灰石即碳酸钙在高温下分解生成氧化钙和二氧化碳,反应为分解反应而非复分解反应;故C不正确;

D、NaOH溶液与稀盐酸反应,反应通过氢氧化钠与盐酸交换成分而生成氯化钠和水,符合复分解反应的特点,属于复分解反应;故D正确.

故选D.

单项选择题 A1型题
问答题

In the latest round of credit-card reforms, issuers and retailers are both playing the consumer-friendly angle. Currently lawmakers are debating whether to cut interchange fees, the tab that merchants pay to card issuers each time a customer uses plastic. While retailers claim they would pass the savings on to shoppers in the form of lower prices, card companies argue the legislation will make credit less convenient and more costly--and they may be right.

Merchants have long complained about interchange fees. They say the costs, which amount to roughly 1.6% of every transaction, erode already razor-thin margins. Last year retailers, the main supporters of three bills now working their way through Congress, forked over an estimated $ 48 billion in card fees. "We can’t keep absorbing these fees," Kathy Miller, a grocery store owner in Elmore, Vt. , testified at a congressional hearing in early October.

In their quest to win over lawmakers, retailers maintain consumers won’t get hurt--and may actually benefit. "Our market is extraordinarily competitive," says Mallory B. Duncan, general counsel of the National Retail Federation, a trade group. "If costs go down, that tends to drive down prices. "

That’s not what happened in Australia, though. In 2003 the country’s regulators cut the average interchange fee to around 0.5 % of the total bill, from 1%. But most retailers never dropped their prices, and credit-card issuers jacked up borrowers’ fees to make up for the lost revenue, according to a report by CRA International, a consultancy. After the regulation was passed, the annual fee paid by cardholders rose by 22%, to an average of $ 25.65. Annual fees on rewards cards jumped by as much as 77% since issuers’ profits took a bigger hit. Australian card companies generally levied a higher interchange fee on rewards cards to cover the added cost of the perk--as they do in the U.S.

Analysts worry that retailers and card issuers in the States would respond in much the same way. Already U.S. lenders have been raising rates and tacking on new charges for borrowers following a ban earlier this year from Congress on certain practices, including late-payment penalties. "When the banks have a major source of revenue eliminated, they need to raise [other fees] to make up for that," says David S. Evans, a lecturer at the University of Chicago Law School.Any new rules could make it less convenient for consumers to opt for credit over cash. As part of the proposals, lawmakers are considering whether to let retailers set a minimum payment for purchases with plastic; they now risk paying a hefty fine for doing so. If such changes are made, customers won’t be able to pull out their cards all the time. Merchants may also have the option of rejecting a specific card, like a reward card, if they think the interchange fees are too high. Currently retailers must accept all products under a single brand such as Visa. "Consumers want to be able to use their card for any kind of purchase," says Shawn Miles, MasterCard World wide’s head of global public policy. The legislation is "anti-consumer. "

Such a defense may work A report by the Government Accountability Office, an investigative arm of Congress, due out by Now. 19, is weighing the potential impact of proposed rules on the care-carrying masses. If the GAO finds that only merchants benefit from lower interchange fees, card companies may win. Says Brian Gardner, a vice-president at research firm Keefe, Bruyette & Woods. "If the report comes out and says there is little evidence that [the benefits] would be passed on to consumers, then I think the oxygen gets sucked out of this thing. \

1.What are interchange fees Why does the author say "issuers and retailers are both playing the consumer-friendly angle" (Para. 1)