鸡蛋壳的主要成分是碳酸钙。某学生想测定鸡蛋壳中碳酸钙的质量分数,取15g干燥的碎

题型:计算题

问题:

鸡蛋壳的主要成分是碳酸钙。某学生想测定鸡蛋壳中碳酸钙的质量分数,取15g干燥的碎鸡蛋壳放入烧杯中,向其中加入了40g稀盐酸恰好完全反应(假设鸡蛋壳中除碳酸钙外的其他成分都不溶于水,且不与稀盐酸反应),反应后烧杯中物质的总质量50.6g。计算鸡蛋壳中碳酸钙的质量分数(结果保留1位小数)。

考点:化学反应方程式的计算
题型:计算题

某旅社有100张普通客床,每床每夜收租费10元时,客床可以全部租出;若每床每夜收费提高2元,便减少10张床租出,再提高2元,再减少10张床租出,依次变化下去,为了投资少而获利最大,每床每夜应提高租金______元.

题型:计算题

认证机构颁发的数据电讯或者其他纪录,是用来确认()的身份。或其他充足的特征。

A、通过网络进行商务活动的人

B、持有特定密钥的人

C、信息的发送者

D、信息的接收者

题型:计算题

Until the late 1940s, when television began finding its way into American homes, companies relied mainly on print and radio to promote their products and services. The advent of television (1) a revolution in product and service. Between 1949 and 1951, advertising on television grew 960 percent. Today the Internet is once again (2) promotion. By going online, companies can communicate instantly and directly with prospective customers. (3) on the World Wide Web includes advertising, sponsorships, and sales promotions (4) sweepstakes, contests, coupons, and rebates. In 1996 World Wide Web advertising revenues (5) $ 300 million.

Effective online marketers don’t (6) transfer hard-copy ads to cyberspace. (7) sites blend promotional and non-promotional information indirectly delivering the advertising messages. To (8) visits to their sites and to create and (9) customer loyalty, companies change information frequently and provide many opportunities for (10) .

A prototype for excellent (11) promotion is the Ragu Web site. Here visitors can find thirty-six pasta recipes, take Italian lessons, and view an Italian film festival, (12) they will find no traditional ads. (13) subtle is the mix of product and promotion that visitors hardly know an advertising message has been (14) . Sega of America, maker of computer games and hardware, uses its Web site for a (15) of different promotions, such as (16) new game characters to the public and supplying Web surfers the opportunity to (17) games. Sega’s home page averages 250,000 visits a day. To heighten interest in the site, Sega bought an advertising banner on Netscape (18) increasing site visits by 15 percent. Online (19) in Quaker Oats’ Gatorade promotion received a free T-shirt in exchange for answering a few questions. Quaker Oats reports that the online promotion created product (20) and helped the company know its customers better.

13()

A.Since

B.However

C.Such

D.So

题型:计算题

克服寄生干扰的方法是().

A.提高输入回路的选择性

B.提高高频放大功率

C.合理选择中频放大方式

题型:计算题

甘味药的作用是()

A.发散、行气、行血

B.收敛固涩

C.软坚散结、泻下

D.补益、和中、缓急

E.渗湿利水

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