问题 单项选择题

True, some of the attacks against whites by blacks are for money and valuables. But, others ale revenge assaults by blacks for a real or imagined racial insult. It is equally true that the vast majority of violent crimes against whites are committed by whites, while the vast majority of violent crimes against blacks are committed by other blacks. Yet even after discounting crimes that are hastily and erroneously (错误地,不正确地) tagged as racially motivated, many blacks do attack whites because they all white. A 1998 Justice Department study confirmed that nearly 20% of the more than 4,000 hate crimes well committed against whites, and their attackers were blacks. The Southern Poverty Law Center also notes that there is a huge escalation in black-on- white violence from nearly none at the beginning of the 1990s.
A collection of white supermacists and rightist extremist groups have eagerly made black-on- white violence a wedge issue in their movement to paint blacks as the prime racial hate mongers in America. The New Century Foundation, an ultra-conservative think-tank, has launched a full- blown national campaign to alert whites to the danger of black hate crimes. These groups and individuals magnify hate crimes by blacks in order to back their social agenda. They oppose affirmative action programs and per hate crime laws. They downplay, or justify, the proliferation of white-supremacist-tinged paramilitary groups, police violence, and racial profiling. And they lobby hard for more prisons, police, and tougher laws.
Black-on-white violence also reinforces white fears of blacks as the ultimate menace to society. When blacks say or do nothing about these attacks, it is taken by some as a tacit signal that blacks put less value on white lives than black lives. This is a terrible price for black silence on hate crimes committed by blacks.

The best topic of this passage is ______.

A. Black and White
B. Black-on-White Violence
C. Security Is an Illusion
D. White Supremacists and Rightist Extremist Groups

答案

参考答案:B

解析:本题是主旨题。整篇文章都是围绕黑人与白人之间的各种冲突(black-on-white violence)展开的,第一段说明袭击事件的各种目的,第二段指出白人至上主义者以及右翼极端分子组织利用白人与黑人之间的暴力冲突发动他们的一系列活动,第三段说明这些冲突增加了白人对黑人的恐惧。因此B选项“黑人与白人之间的冲突”恰当地概括了文章的主题。

实验题

某食用白醋是由醋酸与纯水配制而成,用0.1000 mol/L NaOH溶液准确测定其中醋酸的物质的量浓度。以下为某同学列出的实验步骤(未排序),请回答下列问题。

A.分别向碱式滴定管、酸式滴定管注入NaOH标准溶液和待测醋酸至0刻度以上2~3cm

B.调节滴定管液面至0或0刻度以下,记下读数

C.用NaOH标准溶液滴定至终点,记下滴定管液面的刻度

D.用标准溶液清洗碱式滴定管2~3次;待测醋酸清洗酸式滴定管2~3次E.用待测醋酸清洗锥形瓶2~3次

F.排气泡使滴定管尖嘴充满溶液,把滴定管固定好

G.滴定管检漏,用水清洗所有仪器,备用

H.通过酸式滴定管向锥形瓶注入20.00 mL待测醋酸,并加入2-3滴指示剂

(1)用离子方程式表示该实验的原理                                     

(2)从上述实验步骤中选出正确的并按操作先后排序。你的实验顺序为:(用字母

表示)                                                               

(3)实验室常用的酸碱指示剂有甲基橙、石蕊和酚酞,你选择的指示剂是________,

理由是_______________________________________________________________ ;

滴定终点的现象是______________________________________________________。

(4)某同学实验后得到的数据如下:

           滴定次数

实验数据

12345
V(NaOH) /mL(初读数)0.000.200.000.100.05
V(NaOH) /mL(终读数)15.7515.2014.9815.1215.05
原白醋中醋酸的物质的量浓度为____________mol/L(结果保留4位有效数字)。

(5)分析下列操作对测定结果的影响,用“偏低”、“偏高”或“不影响”填空。

①滴定前碱式滴定管充满溶液,滴定后尖嘴处有气泡_______;

②读取标准溶液体积时,滴定前平视,滴定后仰视________。

单项选择题