问题 问答题

维生素是人体必备的营养物质,维生素D2的化学式为C28H44O.试计算:

(1)维生素D2的相对分子质量______;

(2)维生素D2中的碳、氢、氧三种元素的质量比______;

(3)198g维生素D2中含碳元素的质量为______g.

答案

(1)根据相对分子的质量为组成分子的各原子的相对原子质量之和,可得维生素D2的相对分子质量为:12×28+44+16=396;

故答案为:396;

(2)根据化合物中各元素质量比=各元素的相对原子质量×原子个数之比,可得维生素D2中的碳、氢、氧三种元素的质量比为:

(12×28):44:16=84:11:4; 

故答案为:84:11:4;

(3)根据物质中某元素的质量分数=该元素的相对原子质量×原子个数该物质的相对分子量×100%,可知

维生素D2中碳元素的质量分数=

12×28
396
×100%=84.8%,则198g维生素D2中含碳元素为:198g×84.8%=168g;

故答案为:168.

填空题
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Young adult filmmakers all hope to show their works in international festivals like Sundance and Toronto. But what about really young filmmakers who aren’t in film school yet and aren’t, strictly speaking, eve adults?

They are at the heart of Wingspan Arts Film Festival tomorrow, in a setting any director might envy: Lincoln center. Complete with “red carpet” interviews and various awards, the festival has much in common with events for more experienced moviemakers, except for the age of the participants: about 8 to 18.

“What’s really exciting is that it’s film for kids by kids,” said Cori Gardner, managing director of Wingspan Arts, a nonprofit organization offering youth arts programs in the New York area. This year the festival will include films not only from Wingspan but also from other city organizations and one from a middle school in Arlington, Virginia. “We want to make this a national event,” Ms. Gardner added.

The nine shorts to b shown range from a Claymation biography of B.B. King to a science fiction adventure set in the year 3005. “Alot of the material is really mature,” Ms. Gardner said, talking about films by the New York branch of Global Action Project, a media arts and leadership-training group. “The choice is about the history of a family and Master Anti-Smoker is about the dangers of secondhand smoke.”  Dream of the Invisibles describes young immigrants’ (移民) feelings of both belonging and not belonging in their adopted country.

The festival will end with an open reception at which other films will be shown. These include a music video and a full-length film whose title is Pressure.

56. Wingspan Arts Kids Film Festival _____________.

A. is organized by a middle school

B. is as famous as the Toronto Festival

C. shows films made by children

D. offers awards to film school students

57. Which of the following is true of Wingspan Arts?

A. It helps young filmmakers to make money.

B. It provides arts projects for young people.

C. It’s a media arts and leadership-training group.

D. It’s a national organization for young people.

58. The underlined word “shorts” in Paragraph 4 refers to _________.

A. short trousers  B. short kids   C. short films  D. short stories

59. Movies to be shown in the festival ______________.

A. cover different subjects            B. focus on kid’s life

C. are produced by Global Action Project  D. are directed by Ms. Gardner

60. At the end of this film festival, there will be __________.

A. various awards      B. “red carpet” interviews

C. an open reception  D. a concert at Lincoln Center