问题 选择题

下列说法中,正确的是

A.用标准盐酸滴定待测氢氧化钠溶液浓度,水洗后的酸式滴定管未经标准液润洗,则滴定结果偏低

B.配制0.1mol/LNaOH溶液时,用潮湿的烧杯称量NaOH固体,对配制结果无影响。

C.测定镀锌铁皮镀层厚度实验,当表面镀层反应完后需将铁皮用水洗,然后用酒精灯高温灼烧冷却后称量,以减少实验误差。

D.测定小苏打中Na2CO3含量的方案:取a(g)样品与足量稀硫酸充分反应,逸出的气体用碱石灰吸收,增重b(g)。

答案

答案:B

题目分析:A、用标准盐酸滴定待测氢氧化钠溶液浓度,水洗后的酸式滴定管未经标准液润洗,则盐酸浓度降低消耗盐酸溶液的体积增加,滴定结果偏高,A不正确;B、配制0.1mol/LNaOH溶液时,用潮湿的烧杯称量NaOH固体,氢氧化钠质量不变,对配制结果无影响,B正确;C、测定镀锌铁皮镀层厚度实验,当表面镀层反应完后需将铁皮用水洗,然后烘干称量即可,用酒精灯高温灼烧则导致铁被氧化,引起实验误差,C不正确;D、逸出的气体中除了含有CO2外还有水蒸气,D不正确,答案选B。

判断题
阅读理解

Another small animal that tigers eat in Ranthambhore (a wildlife park in northern India) is the porcupine (豪猪).These animals are spread widely across India in open areas and grasslands; they often live in the earth and between rocks.They are good diggers, and in Ranthambhore are nocturnal (夜出的); they only come out at night.They weigh 12 to 16 kilograms and reach the length of 80 to 90 centimetres.They live usually on vegetables and fruit and seem to have a good sense of smell.Porcupines defend themselves when attacked by moving backwards with their quills upright, often making a strange noise.

Several times, I have found the remains of quills where a tiger has killed and eaten a porcupine, but I have never actually seen the kill.In spite of the quills, experienced tigers will try to kill clearly by biting the porcupine’s head, its weakest spot.But the quills are very sharp and can give painful injuries to young tigers.If the quills have gone in very deeply or if they are stuck in the tiger’s paw, it will try to pull them out.Often, it will be successful, and the wound will get better.But, if the quills have gone in very deeply or if they are stuck in the tiger’s neck or mouth, where they cannot be reached, the wound will often turn bad.If this happens, the tiger is in pain and is less able to hunt animals.It has to look for easier prey and so may turn to cows on the edges of the forest.From this, it is a small step to becoming a man-eater.

小题1: A porcupine is a small animal which _____.

A.likes to stay on vegetables and fruit

B.eats nothing but vegetables and fruit

C.prefers to stay on vegetables and fruit rather than anywhere else

D.has vegetables and fruit as its main food小题2: The word “quill” here means ____.

A.teeth of a porcupine

B.feathers on a porcupine

C.long, sharp needle-like parts on a porcupine

D.paws of a porcupine小题3:According to this passage, what causes a tiger to become a man-eater?

A.When there are no porcupine for a tiger to catch.

B.When it turns to cows on the edges of the forest.

C.When a tiger wasn’t hurt seriously.

D.When it is difficult for a tiger to catch other animals.小题4:What is the proper title for this passage?

A.A Tiger and Its Food.

B.How Do Tiger Kill Porcupines?

C.What Can Cause a Tiger to Become a Man-eater?

D.A Porcupine.